Humans are really hard to do. I think mostly because you have the challenge of doing a non anime drawing which is hard to get away from when you watch it all the time and are working on it digitally. Also when you do animals or anthro you dont really have to fallow any rules, whatever you do to it ends up looking intentional when if you mess up on a human or looks wonky
It's true, why art teachers hate when you do anime work, they should just say don't do too much stylized work because it makes realism a bitch later on! But like all art, it's just a matter of practice and I discovered something called speedpainting which helps!
That's why I wanna be an art teacher man. Seriously I hate art teachers. I only had one that was worth anything and he inspired me to be an art teacher. They suppress your art too much. Which is opposite of art