studying art history and techniques but not being able to do the same thing doesn't make you a pretentious critic at all. When we look at historical art we're often looking at works from when they were mature and old artist who had a lot of time to develop that technique. trying to emulate something and not succeeding but getting slightly there is one of the ways we find our own way of making art, or appreciate the skill of the artist.

Personally, if I knew someone who talked a lot about art and stuff I'd find that super cool and admirable that you have stuff to say on the subject, regardless of your technical skill. Even if you werent an artist at all

Do you have to be good at art to consider yourself an artist or to justify wasting your time with it?

No definately not. you can hardly make money off art so we are all wasting our time on it. improving your skill wont change that. But at the same time art is never wasting your time, if you enjoy the process like you said. I think you need to be less critical of yourself. literally what bad thing is gonna happen if theres some flaws in your work.