hey there! i know i'm a stranger to you but i wanted to give you advice.
art isn't easy: it never is, and even as you "improve," things will always be difficult to perfect and fit your idea of "good." i'm gonna address everything you said in your post, alright? firstly, i don't think you should draw if it makes you unhappy. art is a form of expression — the process matters just as much as the end result. if you focus so much on how it will look in the end, there's no point! you have to have some enjoyment in art. i guarantee if you have fun while you draw something, at least you have that joy out of it, so please don't draw if it damages you that way. however, i do not think you should quit art completely because of this. i understand. i was once — and still am — in a position similar to yours. i never thought i was improving, even though i drew/draw daily. this is what i thought many days for many years — i have been drawing for six, ever since i was ten. i'm only a year older than you, sixteen, and i know you said that people your age or around your age are "better than you," but it's no use to compare yourself to them! everyone's at different skill levels — based on when they begin, how much they practice, and heck, yeah, some people are just naturally "gifted" at it.
you can't "literally not improve." that's just not how that works; just draw. draw what makes you happy, draw if it makes you happy. don't force yourself to draw if it doesn't, otherwise you won't be satisfied. take parts of others' art that inspires you, not get jealous of it — instead of telling yourself "they draw much better than me," tell yourself "i'll work to achieve a level of skill like theirs." don't put yourself down. again, art isn't easy — but if it's something you're passionate about, something that brings joy to your life, keep pursuing it. be proud of the things you draw when you're proud of it. that's one of the many joys art can give you.
i'm sorry for the lecture btw uhuh... i think your art is so adorable!!! <333 i love the anime style since im an anime geek myself haha, keep up the great work my friend!!!!!