[No Spoilers] Why did TLOK receive so much hate?

Everywhere I go I see loads of content (video reviews, discussions, articles...) aimed at qualifying the legend of Korra as a show that sucks/is bad/doesn't deserve to exist and whatnot. Even the comments I see one videos regarding TLOK that aren't made with this point tend to be, even if mildly, hostile towards the show and most things in it.

Can someone explain to me why this is the case?

EDIT: Beware, there are some major spoilers of Book 4 on the comment section.