It's when I click into an interesting topic, and it's steered into being an offtopic retread of every other thread about US politics. The upvote/downvote system simply no longer works to squelch it as it once did, because there are enough people here who believe "everything is political" and therefore it's always "on-topic".
That is their prerogative, but it has dramatically lessened my enjoyment and engagement on this platform in the last 5 years. And it's gone into overdrive in the last 6 months.