At first it was all about presenting data in an original looking way. In the end it was about pushing political ideas in your throat using a plain bar graph. It was not about sharing something interesting you found but about taking advantage of a captive audience.
There’s quite a few but I’ll give my top 3:
r/TIFU and r/AITA - The former became a repository for preteen fanfiction and the latter became a place for confirmation bias/rhetorical questions looking for validation.
Then there’s r/UnpopularOpinion which ended up being an oxymoron unto itself. I honestly don’t understand how anyone thought that concept would work given that the literal point of a social media discussion platform, that utilizes an upvote/downvote system to determine visibility, is to push popular (highly upvoted) posts to the top/front. Very few people actually upvoted something that was unpopular and instead just upvoted the low hanging fruit popular opinion posts that were ‘controversial’ but still blatantly have a clear majority who support that side that OP took.
r/UnpopularOpinion became a place to either validate some truly reprehensible views or say something well liked for internet points.
Most of AITA was fanfic too - just a deeply improbable amount of twins, pregnancies, weddings, and twin pregnancies at weddings. Once I stumbled upon a megapost that was all the ones about food, though, and it was great, because nearly no one bothers to make up a drama about lasagna.
The one silver lining was it brought us the glory that was the “everything in this sub is fake” punchline story, if anyone else remembers that one.
Imo even with how the downvote/upvote in Reddit work, theoretically speaking there could be ways for r/unpopularopinion to work with some configurations. For example, automatically delete any post that gained a certain amount of upvotes. It’s understandable that upvotes should be given to unpopular but interesting opinions that actually fits the sub, but since it’s been shown that’s not how people do it that behaviour should have been used to keep the content relevant.
Change the css so that hitting the up arrow downvotes and hitting the down button up votes. The users could use the voting buttons as usual but the unpopular posts and comments would be pushed to the top.
A sub “the tenth dentist” (I forget the specific name) had a system where if you agreed with it you down vote, whereas if you disagree you upvote. I think it made moderation probably kind of tricky (they also had a way to flag things as hugely improbable/karma farming) but it at least kept the spirit of truly unpopular opinions at the forefront.