When I studied photography, many of my teachers would share with myself and fellow students why a photo didn’t quite work, what would help, be it little or large. No-one on redbubble offers any constructive criticism. It’s a little bit ‘Disney’. I wouldn’t go slit my wrists if some-one suggested an alternative appreciation of an image i’d captured.
I suppose it’s a little like “If you can’t say something nice, don’t say anything at all.” However, I don’t think you are a bad person for suggesting that a picture of someone’s fucking pussycat should maybe not ‘cut it’ on a website that claims to be an ‘Online Artistic Community’.