The awful moderation is by far the biggest problem. It's so frustrating to ask a perfectly good question, get some good answers to it, and then later on some micropenised moderator comes along and starts muddling with the questions and answers just to make himself feel like his micropenis isn't as small as it is.
Yeah, I've never used SO heavily, just occasionally. But over the last few months it does seem like fully half of the few queries I have that lead me to SO, are closed as "not relevant to programming", despite being obviously 100% relevant to programming. Seriously, what kind of jackass moderates a question about setting network call timeouts FROM CODE as not being about programming.
I know it didn't used to be that way, because it was only in 2015 that I encountered the first obviously incorrect, probably malicious, "not relevant" moderation. And it has grown to be all the damn time now. I used to be happy when google put an SO question at the top of my responses because it was likely to provide good info, now I'm starting to be annoyed by it.