Aye, I was a bit late to respond because I had to sleep, but copying is one of many tools you should be using! It's a VERY underrated tool (for good reason unfortunately, places like DeviantArt have some pretty shifty reputations for misuse of the technique), but it is by far not the only one you should rely on lest it becomes a crutch. This is true of anything!
Also, don't copy from pixel art , copy from life! Good stylization for me always came in three big steps:
-learn anatomy and basics like shading complex shapes
-study how other people stylize and twist out from that base of understanding
-tear off bits and pieces of those styles to create my own frankensteinian hodgepodge of my own, because nothing is actually original and everyone is inspired by something
The former is the MOST important to learn, in my opinion, since it drills into you a sense of consistency and understanding of 3 dimensional space. Construction is also a big thing you pick up.
Again, start with traditional and practice exercises. There's a whole world of artistry information out there, do what I did and start bingeing on art technique guides scattered through the internet! Your process may vary wildly from my own, and I encourage you to explore that since that's simply the way it goes!
Just don't be too afraid to jut out of that comfort zone! if you start getting frustrated with your art that's a sign you're able to see the old flaws better now, meaning you're on your way to fixing them.