This. To add; constructive isn't that hard. Even if something's a C+ story, did something make you laugh? a scene evoked an emotion? was there a clever turn-of-phrase? did you recognize the obscure (or niche) reference? supporting character did something interesting? a setting you know well? or that's new to you?
Because how could we know if new author is brass-balls confident or has nervously overcome self-doubt? Or is an established author experimenting under a pseudonym?
Further, I'm following a few stories here that have a smallish group of commenters; but they're the right group of commenters. People that know the setting, like the tempo, get the references, and appreciate the genre. That's pretty awesome, and sometimes you can have a better conversation with six than with 300. So that's cool, too.
I'm very much with @Krista and @Mark Arbour that I'm here for what GA is, and I don't think I'd like change that wasn't organic growth.