They SEOd their way into being a top search result by showing crawlers both questions and answers, but when you visited the answer would be paywalled

Stack Overflow’s moderation is overbearing and all, but that’s nowhere near at the same level as Expert Exchange’s baiting and switching

the gatekeeping, gaming the system, capricious moderation (e.g. flagged as duplicate), and general attitude led it to be quite an insufferable part of the internet. There was a meme about how the best way to get a response is to answer your own question in an obviously incorrect fashion, because people want to tell you why you're wrong rather than actively help.

Often the answer to the question was simply wrong, as it answered a different question that nobody made. A lot of times you had to follow a maze of links to related questions, that may have an answer or may lead to a different one. The languages that it was most useful (due to bad ecosystem documentation) evolved in a rate way faster than SO could update their answers, so most of the answers on those were outdated...

There were more problems. And that's from the point of view of somebody coming from Google to find questions that already existed. Interacting there was another entire can of worms.

That despite their url's claim, they didn't actually have and sex change experts.