How do I get good at animation even though I'm not good at drawing and digital art?
Hard work. One does not become a god in animation overnight.

Learn to master Illustrator, Photoshop, After Effects. That's virtually all you need for professional animation. Or go and look for programs that fit your workflow best and stick with them. Don't try to be "moderate" at every program, master your few.

There are great books and masterclasses and guides on sites such as pluralsight. Create something, realize it sucks, do it again, improve. That's the natural way all of us had to learn design, animation, compositing etc.