CONSTRUCTIVE criticism

I have to get this off my chest. I hate it when people leave criticism, for the sake of it. Without any real feedback.
I say this today, because on one of my stories, I got two very similar comments;

"You're OC is a Mary-Sue"

And that's it!
I don't entirely see how she's a Mary-Sue, and they don't explain how she is, or how I can stop her being one. No. I just get "MARY-SUE!"
What do you want me to do about it?
"NOTHING! I WANT YOU TO CARRY ON SO I CAN KEEP TELLING YOU HOW SHIT YOUR OC IS!"
Thank you helpful reviewers.

Something I've spotted that these two commenting baboons have in common... One doesn't write stories at all, she's just a reader. The other has never created her own OC ever, she writes stories about pre-existing characters.
Sorry, but give it a damn try before criticising others, creating an OC is pretty hard, and nowadays everything an OC does can lump them into the "Mary Sue" category.

/le sigh

I feel quite disheartened and want to quit that story now. I've gotten a lot of positive feedback on that story, but seeing as I'm fighting a losing battle here, why continue?