An interesting case here is Craigslist. I won’t say their UX is poor per se, but it’s very much a matter of taste that not everyone shares. Notably, the Venn diagram of their user base and the people who vocally laud their UX is likely an enormous circle with a competitively tiny one hiding inside it (respectively).

I think it’s interesting because while I personally don’t like the Craigslist UX, I have no objection to using it anyway (even if might I try other solutions first). They provide enough other value to me, and the UX is good enough, that I still have an overall positive impression of the service.

I also find it interesting because the debatability of their UX is really very surface level. There are all kinds of things I wish were different, but that’s mostly because it was perfectly fine in 200* and hasn’t much changed with the times beyond a few utilitarian niceties.

I’m sure this is way overly specific to CL as a reply, but your comment about UX focus resonates with me, and I’ve long found Craigslist’s lasting success fascinating in this light.