I think Mint gets shit on because it's based on Ubuntu (which already gets shit on a lot) and only gets a new release when the Ubuntu LTS does, so it's kinda out of date.
Rolling release distros get recommended over it a lot because having a newer kernel gets you better gaming performance and a lot of the techy people who'd even care about switching, also like gaming. And nowadays, immutable distros get recommended a lot so you can't fuck things up with a weird config change. Mint just doesn't do anything significantly better than any other distro, it's lukewarm.
I don't think the desktop environment actually has much to do with why people dislike Mint. It's just fine IMO. I'll take it over Ubuntu, but these days I'm on OpenSuse Tumbleweed. Rolling release, and comes with snapshots configured straight out of the box so when I fuck something up, it's fairly quick do undo.