Fuck "pretentious".
It gets my nomination for World’s Worst Word. Sure, there are a lot of obvious competitors; words people consider inherently offensive that get used pretty horribly all the time, but that's actually why this one wins: despite its more benign nature it beats out most others in the consistency of its horribleness.
I don't know. Maybe there's a whole society of much smarter people out there who use "pretentious" in somehow perfectly valid ways on a regular basis. But I don't think I've met them. My experience is that 98.65% of uses of the word pretentious are in fact incredibly pretentious, far more so than anything they could be talking about.
Because what are you doing when you call something pretentious? You're saying its creators (or fans, perhaps) are imbuing it with an importance it doesn't deserve - that they're being somehow disingenuous in their appreciation of this thing. I usually see it in reactionary responses to fairly niche products that most people don't like; the idea generally seems to be that because Bob doesn't see any appeal in the widget, Alice must have some ulterior motive for liking it. Often there's some accusation - implied or explicit - that Alice "just wants to look smart/edgy/cool". It couldn't possibly be that Alice simply has different tastes to Bob due to a different set of life experiences, and that both tastes are in fact valid. No, Bob has to imbue his opinion about Alice's motivations with such importance that it outweighs Alice's rebuttals, when one would think she should be the authority on herself. But Bob's opinion is a guess, it's unfounded, so it can't possibly deserve the importance he's giving it, and so he's making a pretentious statement, based on his imagined expertise at judging others/mindreading.
And I don't get it. Is it actually difficult to acknowledge that some people like things, some people don't like them and that's okay? You can have really interesting, human discussions about all the reasons why you each feel the way you do without resorting to nonsensical and insulting guesswork about each other's intentions. Give people the benefit of the doubt, internet.