When you say "does a decent job" the question is compared to what ? If you are genuinely satisfied with the output of your printer, That is what counts the most. If you are interested in showing the maximum possible quality available from a camera like a D850, the answer is you can do significantly better.
True large format , wide Gamut photographic printers can make really wonderful and noticeably superior prints in an optimized workflow. Which includes providing an optimized file --usually a 16bit TIFF in the appropriate color space, and density.
Many labs work mostly from JPEGs which limits your color space to sRGB. The D850 files can exceed Adobe RGB.
However it is unlikely that any file you send to a lab will be the best possible file for the way they are set up. That's why people 'soft proof' to dial in an optimized file, or have printers controlled by RIP (Raster image Processor) software like Image Print.
If you are serious about getting the best quality, pick a lab that Accepts TIFFS in at least ADOBE RGB and speak to them about making some test prints. Once you dial in your file prep and you get good tests, order the big print and then stick with that lab. (---You may be able to try soft proofing in your editing software)
The most important thing is how much effort you want to put into the process. There is no wrong answer, they are your prints and it is your money. Very nice prints can be made from JPEGS. Depending on the file, not all pictures necessarily need a wide gamut printer, others benefit a great deal.
It takes time and effort to find out.
The best place to start is by looking at great prints.
Like many things, getting to 80% of possible quality is easy, getting to 90% is much harder, above that Harder still.
Nowadays, 80% looks very good vs any historical comparison, but you will know when you see the really good ones.

Ex digital/film lab product manager here...

Lab prints are not necessarily sharper or more saturated or vivid than inkjet prints made on quality inkjet printers with OEM ink and real inkjet photo paper.

> Silver halide wet process papers have about one fifth the dye stability of pigment inkjet prints.

I have silver halide prints kept in dark storage for 20 years that have faded significantly, and I know they were processed correctly. They were done in our lab! I recently made a 45th year reunion video slide show for my college class, so I saw a lot of 45-49 year old photos that look terrible.

> High end pigment inkjet prints can be made on MANY different types of papers, plus cloth, canvas, and other substrates.

From high gloss coated photo papers to standard 'E' surface paper similar to Kodak Portra, to archival quality cotton rag paper that is absolutely the most matte surface you ever saw, there is something for everyone.

> 90% of digital image quality comes from how you prepare — post process — your files.

Hopefully, you begin by saving raw files at the camera. Post processing raw data gives you FAR more latitude to control color and tones.

If not, hopefully you know professional exposure, white balance, and menu tweaking techniques for achieving great JPEG images in the camera.

Hopefully, before any color and tonal adjustments of your files, you calibrate and profile a photo quality monitor capable of at least P3 color gamut. This requires a software plus hardware solution (kit) from either Datacolor or Calibrite (formerly X-Rite). When using labs, calibrating your monitor is the single most important thing you can do before making ANY adjustments, if you want the best pricing and the best results at the same time, and consistently.

Hopefully, you COMMUNICATE well with your chosen lab, and follow their advice regarding color management and workflow. Typically, they can provide you with ICC profiles for their specific printers and papers, so you can use them as "proofing profiles" or "simulation profiles" to see what your finished prints will look like in your post production software, AS you are doing your final adjustments.

There are MANY great labs in this country. I'll name a few... Bay Photo, H&H, Millers/Mpix, WHCC (White House Custom Color), Full Color, American Color Lab, American Color Imaging, Nations Photo Lab, UPI lab (United Promotions, Charlotte) ...and if you want more, then do a Google search, using 'professional photo labs' for the search criterion.

Modern pro labs do serve different market segments such as commercial advertising photographers, school portrait and event photographers, "mom and pop" street corner studios, arty photographers, art museums doing copy work, photojournalists, etc. Some do a wide range of work.

Others specialize in high end inkjet work or "gicleé" printing. Gicleé is a made-up term invented to disguise the fact that it's inkjet printing. In the late 1990s and early 2000s, professional inkjet printing was confused with crappy office and home inkjet printing in the minds of most people, so there was a very undeserved stigma. There is NO REASON to doubt the quality of high end inkjet prints made on Epson and Canon photo printers. In almost all cases, I would rather have a big pigment inkjet print than a big silver halide print. It will COST a lot more, but it is worth it. You get a much wider color gamut and five times the print longevity because transparent dyes fade, and pigments are solid colors.

I hope this helps. Both labs and home/studio printing have their places. But the prep for both is the same if you want high quality. Setting up your workflow correctly for one will eventually satisfy the other, once you learn finesse.

When you say "does a decent job" the question is compared to what ? If you are genuinely satisfied with the output of your printer, That is what counts the most. If you are interested in showing the maximum possible quality available from a camera like a D850, the answer is you can do significantly better.
True large format , wide Gamut photographic printers can make really wonderful and noticeably superior prints in an optimized workflow. Which includes providing an optimized file --usually a 16bit TIFF in the appropriate color space, and density.
Many labs work mostly from JPEGs which limits your color space to sRGB. The D850 files can exceed Adobe RGB.
However it is unlikely that any file you send to a lab will be the best possible file for the way they are set up. That's why people 'soft proof' to dial in an optimized file, or have printers controlled by RIP (Raster image Processor) software like Image Print.
If you are serious about getting the best quality, pick a lab that Accepts TIFFS in at least ADOBE RGB and speak to them about making some test prints. Once you dial in your file prep and you get good tests, order the big print and then stick with that lab. (---You may be able to try soft proofing in your editing software)
The most important thing is how much effort you want to put into the process. There is no wrong answer, they are your prints and it is your money. Very nice prints can be made from JPEGS. Depending on the file, not all pictures necessarily need a wide gamut printer, others benefit a great deal.
It takes time and effort to find out.
The best place to start is by looking at great prints.
Like many things, getting to 80% of possible quality is easy, getting to 90% is much harder, above that Harder still.
Nowadays, 80% looks very good vs any historical comparison, but you will know when you see the really good ones.

I don't think sharpness should be any different if you have a good home printer. Maybe if you use a magnifying glass.
But before you send a print off to a photo lab, make sure they are using a silver halide professional printer. Otherwise you will just be getting an ink jet print.
The color gamet should be much better because an inkjet printer is only as good as how many ink jet cartridges it has (cyan/light cyan, magenta/light magenta etc.).
A professional silver halide printer uses a laser capable of millions of colors reproduction. Also, silver halide paper will give you a much better print.