When reading my reply, please take into account that I have no clue about your level of knowledge.

Here is my answer to a similar question at another location.

Cropped or full frame sensor?

Some argue that there's no need, or very little use, for more than 20MP. Others disagree.

The sensor...
A cropped sensor is smaller than the size of a full sensor. A full sensor is 36x24mm's. The full frame sensor size comes from, is the same as, the era of 35mm film.

So if a cropped sensor has the same amount of pixels as a full size one it means that the full frame sensor has bigger/larger pixels, and vice versa, when compared.

This has an impact in some picture quality.

In general these two sensors have distinct differences. If the two sensors have the same amount of pixels, the cropped sensor produces a sharper picture as the pixels are smaller than a full frame sensor. This means that if you shoot full frame you might experience a higher level of grain in your pictures. However, with experience comes the better quality. So if you ever buy a full frame camera you will eventually learn to shoot without the grain disturbance.

On the other hand a full frame sensor responds better to light which means that you can shoot at higher shutter speeds without losing picture quality.

Furthermore, a full frame sensor has a smaller/shallower depth of field than a crop sensor. Sometimes this smaller depth of field is preferable, sometimes it is not.

So what you lose on the carousel you gain in the rollercoaster.

In order to answer your question; I'd say that Yes megapixel count is important to some extent. In general, the higher the amount the better the picture quality, but not without consequences...

From my point of view I no longer see the need for me to get a camera with more than the 24MP I got. I see no justification for the heavily increased cost.

No matter how much I want a Pagani Zonda, a Koenigsegg, or a MacLaren F1 I will never get one. Far more reasonable is getting a Fiat 500 Abarth. It's the same with the camera. No matter how I could crave for a professional Nikon I will settle with the D5300 I have. Because it's the best one I could find that suits my interest and economy.

Now, comparing your phone camera to a real one is another story. Your phone camera is very capable, there's no doubt about that. But it has its limitations. You can't print quality prints in large formats. This means that nor can you zoom in on it for cropping parts out. This is a consequence from the tiny sensor size, and from the amount of pixels it has.

More here:
https://www.slrlounge.com/the-truth-behind-the-megapixel-myth/

Comparing DX vs FX photos:
https://youtu.be/XFncHWMuWX0

Here are two different, refreshing, views on the topic from two professional photographers. Both arguing that it’s not about size, but all about pixel density.

https://m.youtube.com/watch?feature=youtu.be&v=PHYidejT3KY

https://youtu.be/B9be2mrOOJg

—

The added picture of the ship is shot by Jim Stascavage, with a Nikon D7200, it's a 24MP cropped sensor camera.
- Seeing this ship covering an entire wall, I see no need for a full frame camera. Far better is to learn to use the one I have, and spend my hard earned money on lenses instead.

After camera purchase I recommend you read
- "your camera model" For Dummies.
- Stunning Digital Photography by Tony Northrup.
- Secrets To The Nikon Autofocus System by Steve Perry. If it's a Nikon you got.
- Understanding Exposure by Bryan Peterson.

Secrets To... is my favorite, with Understanding... coming up as second.

http://backcountrygallery.com/secrets-nikon-autofocus-system/

All are well invested pennies.

A bad photographer will take bad pictures with a good camera. A good photographer will shoot good pictures with a lousy camera. It’s not about the equipment. It’s all about what is behind it.

https://www.demilked.com/pro-photography-cheap-camera-phillip-haumesser/