I'm of a divided mind on this. On the one hand, as a rule I'm against passing judgment on fic. Among a host of other issues, not only is it discouraging to a writer to be told that they're writing badly - it also can be painful for a reader to be told that what they like to read is considered to be crap, by some wacky subjective definition of "good writing". And since there are definitely people who enjoy reading as well as writing Mary Sues, and they're not actively harmful, then I say more power to those who like them.

On the other hand...for all that some fans are very anti-Sue, and there are folks who flame over them and complain about them and comms devoted to sporking them...I don't know if this is really such a terrible thing as all that. A lot of us don't like 'Sues - they're just not what we read fanfic for, or aren't anymore. And yes, some fans can be bullies, targeting those fans who write what they personally dislike, but that's not news; the cult of mean and the quality control fans are always going to be here. For all that Mary Sue is oft-targeted by such, she's hardly an endangered species. There are plenty of places where Sues are written and posted and welcomed (much of ff.net!) There are tons of young and some older writers writing them, and even if some of them stop, there will always be new writers writing them. The reason we have the phrase "Mary Sue" is because it's a phenomenon that's been going on, well, as long as humans have been storytelling, I imagine, and will keep going on whether or not that word for it falls out of disfavor.