Oh I don't mind leaving actual concrit at all. I love to give concrit and advice and I try to bring out positives, along with the negatives, no matter the skill level. Because there will always be a positive somewhere.
What I have issue with, is how they frame it and force it upon me. I want to give advice when I want to. I want to post my art when I want to. I don't want to be forced to do both every time. When I post my art, I'm okay if people don't comment on it. Yeah, it can be a little bummer sometimes, but when there are a ton of artists, you can't expect every single one to get attention.
They also make it out to be that, if I just want to post my art and I don't comment, I'm an asshole. Despite how much I may do for the server, it's an "asshole move" just to post my art. I don't need that sort of guilt tripping manipulation to compliment someone and it makes me want to do it even less.
I also don't like throwing concrit at people when they don't say they want it. Purely because I've had shit flung at me for doing so, even though I tried to sugar coat things as much as I can with touchy people like that.
It mostly boils down to one of the admins being really insecure over his own art. It's not a rule for the community, but simply because he feels underappreciated for what he posts. That's not even speculation, he said it himself in a side chat.
It's not that I don't understand the desire for validity. Far from it. But guilt tripping me into doing so, and thus forcing fake, soulless, minimal compliments left and right... That shit isn't going to help anyone. It just encourages me to post less. I don't want to participate in the hugbox circle jerk. I just want to post my art. I don't need the added stress of complimenting another drawing every time I just want to share the hard work I did.