Its typical of almost everything now. People don't care about their jobs and do the minimal amount necessary. The companies who employ them pay as little as possible and do not train people well.
That's why forums are so popular. The people who take pictures know more about certain problems than the manufacturers. Also the camera companies do not want to admit their problems even exist.

I had some mail misdelivered, here in the USA. One of the people responsible for sorting the mail did not read English. He put my mail in the wrong slot and it got lost. Eventually they found it

I agree with no12mo, above. Some people are sensitive to noise and for other people they don't care or even like noise.

It also depends on how you view your photos. Are you viewing at 100%. That means you are looking at images at a very large size and you will notice noise more. If you are looking at images at 25% there will be a big difference. Same with prints. 8x10 inches. No noise. Make 30x40 inch prints and look at them from a few inches away and they may look noisy or fuzzy.

You might try experimenting with settings on your camera. Increase noise reduction, but may slightly reduce sharpness or reduce noise in software like Photoshop. Etc. Also reduce or turn off sharpening, that shows more noise. Also do not underexpose images. A lot of the noise is in the shadows. When you lighten images to compensate, you are adding noise.

Does not seem like it should be an issue. Most modern cameras with your size sensor, should be fine until ISI 1600 or 3200.

If you are shooting in a lot of dark environments, use flash or a tripod if possible.

It's a matter of what works for people. Very few people print large prints 16x20 and up. Many people do not print anything.

I was at an amusement park, before the virus shut it down. Hundreds of people, taking photos of their kids, the rides, etc. Me and one other person using a more professional camera.

I see lots of horrible photos. But the people who take them, do Not think they are horrible. They look just like the other photos they see on Facebook and the phones of their friends.

And cell phone cameras are of good enough quality for viewing online and making small prints.

Between the general public not buying better cameras and the slow down of camera sales due to the economy and covid virus, camera companies are suffering. Some will eventually go out of business or make major changes.

I wish more people had respect for serious and professional photographers, but they don't. I recently met someone at a party. As usual, he asked what I did. I told him I am a professional photographer. He told me he did not know any photographers were left.

He told me his family used to go to a local pro years ago. But they stopped and now took photos with their phones. He said the quality was ok, not great, it was convenient and it was free. And he could just post a picture on Facebook for everyone to see. No more mailing prints to everyone.

Times change. A few years ago, people told me how much it meant to them that they had great pictures of their grandmother, etc. She passed away and the memories are important. Now it is rare for families to hire me.

Use the camera. Take a photo, look at the screen and make adjustments. Takes a little practice, but not difficult..I have two Sekonic light meters and almost never use them. I sometimes use film and use a digital camera as a light meter and also to see a "proof". The meters in most digital cameras are also excellent. If the subject allows you can also set up bracketing. If you are close in guessing exposure and even off by a stop or so, one if the bracketed shots is probably fine.

I have a D300 and it is a good camera within certain limits. No video and it's best to keep ISO at 800 and below for best results. You can make a nice 16x20 inch print. So it depends on the needs of the photographer. I now have Fuji equipment. Much lighter, can shoot video and ok to ISO 3200 or even higher. The D300 is old technology but is a bargain in some ways and may work for some people.

Just use your 24-70 for most photos. Being able to zoom is very helpful for candid shots of kids. Both of your zooms are sharp and in low light your D850 will be good to high ISO's like 3200 and even higher. The main advantage of the prime lenses is lens speed and bring lighter in weight.

It's not complicated. It's like selling many other products or services. Like phones. You can buy a new phone for $39 at Walmart or spend $1000 plus. It depends on the client, their needs and budget.

Same thing. Let's say you take a portrait for a client. Does he/she buy a CD with unretouched digital files for $25 or $50 or do they buy a 30x40 inch print on Canvas or Metal for $2,000? Of course it depends on your sales ability and is the client the right one for your business.

Of course lots of people want something for nothing. But high end clients do spend money for personal portraits, photos for their businesses, fine art for their home, etc

If you've sold airplanes you know not everyone buys a plane. I assume most people who buy are corporations, rich people, etc. You don't try to sell planes to the guy who works at Walmart or McDonalds. Yet there may be money in selling them $39 phones (if you could sell enough phones)

You have a substantial investment in Nikon lenses. Unless you have an important reason to change brands, stay with Nikon. Their cameras and optics are excellent.

All the brands from Nikon to Sony to Canon, etc. make great products. Concentrate on taking great pictures, it's more important than the minor differences in the camera brands.

I think your photos are good and will get better with practice and hard work. If you looking to make part time income, start with that and see how it goes. Start with mostest pricing and increase prices every 4-6 months.

I don't know your financial situation, but be aware it can take 2 or 3 years or much longer to create a successful business. Your pictures must be good and marketing must be great.

A very successful photographer I know is actually just an ok photograoher.. But he's excellent at sales, networking and has a great website. Almost everyone who comes into his studio to talk with him about wedding and portrait photography signs up with him.

There is a lot to learn.

I usually advise people to have a stable source of income (a regular job) and to do jobs like portraits, weddings, etc on weekends. And be careful of expenses.. No need for expensive cameras, studio rent and lights when you start out. As you make money, invest conservatively in equipment.

Good luck.

In the studio, when I shoot film, I use a digital camera as a light meter. I can see if the exposure is correct and also check the lighting, composition, color, etc. It's like a Polaroid "test shot". Outdoors with film I will use a light meter with my 4x5 camera. I have found that my Nikon F3 film camera meter is as accurate as my sekonic light meter.

I have both 4x5 and 35mm film cameras. I rarely shoot film anymore. I like shooting color and the cost of 4x5 color film and processing is very high.

The look of film is great, but the time required to shoot 8 shots of 4x5 black and white, process and scan the film is hours. I process and scan my own b&w.

The quality of film is fine, but digital is also great. In my opinion, digital far exceeds 35mm film and equals or surpasses medium format. It is even close to large format. Of course this is my opinion and a lot depends on the film, scanning or printing, etc.

But there is more to it than sharpness, etc
I enjoyed shooting film. The tonality and look of film is different than digital.

I create professional portrait photographs and thought my clients would appreciate film and a different look. But they hated posing in front of a view camera. You need a lot of patience and of course you can not see the pictures for several days, etc. I noticed the difference in how skin is rendered (more softly) and the beautiful tonality, but my clients did not notice this as much as I expected Most important to them is their expression, the outfit they wore, etc. With a few exceptions, they did not want to pay extra to cover the costs of film, processing and scanning.

Do what works for you. Film is not magic just a tool to express yourself. Same with digital photography.

I started to use an Android phone about 2 years ago. It is fun and easy to carry etc. For many things it is fine. I liked using it so much I started to look for a camera that was small and light weigt. I got a Fuji X-T30.

Much lighter than my Nikon and I use the LCD screen to frame photos like my phone, etc. But the inage quality is much better than any phone. Works great at ISO 6400, has a zoom lens, focuses and shoots very quickly and I can enlarge photos to very large sizes. Not exactly a phone experience, but a good compromise.

I have a Fuji X-T30. I have minimal experience with Acros. I have shot Acros film and also the simulation. I don't think the film simulations really match real films, although they can look good. I used Kodachrome film for years and Classic Chrome is not the same. I like the Astia film simulation, but it is certainly different than the pastel tones the film had.

I sometimes use real film, but I decided I like the overall quality and convenience of digital better. I stopped worrying about matching a film and accept the look of digital. Either digital or film can look great, but are different.

If getting an exact Acros look is important to you, use the film. But If getting good, digital black and white is what matters get experience with Photoshop and other programs. Capture One for Fuji is free. It offers a Acros simulation and other simulations.

I have the free Capture One version for Fuji. Works well, great color, not hard to learn. Not sure if I will upgrade to the full version.

They have tutorials on Youtube so you can learn the program and see the features.

I recommend Capture One. You can try the trial version and see what you think.

Most software have a free trial. Do that before you buy. Everyone's needs and preference vary. What works for me may not work for you.

I used to work for Epson, they charge hundreds of dollars per gallon for ink.
But it is similar for Canon, HP, etc. Most home machines have 1/3 of an ounce
of ink in a $20 cartridge. Some have less. Depending on the machine, you
can pay $100 or more for a set of cartridges.

Lots of factors, the photo and the color in it, the printer, settings, etc.
but as a rough guide, figure it costs about $2 to print an 8x10 for ink and paper.

I have owned 4 Epson printers. They work well most of the time and can print
great quality pictures. However, sometimes the printers have problems. Repairs
are very expensive. Usually cheaper to throw out the printer than to fix it.

I often take my photos to Costco and also occasionally to online or pro labs to print.
Usually costs about the same (with Costco, it is cheaper) to print as doing
it yourself. Also to get good prints, it helps to know Photoshop, color calibration
of your monitor, etc.

If you have a few days available to get the prints, send the files to a good lab,
pay a little extra to let them color correct and mail them to you.
Unless you are an expert, their prints will often be better than
the prints you make yourself.