Weird formatting, things not working and you not remembering/understanding why, trying to keep settings in sync across browsers and platforms, and so on.

IOW I've found it easier to tolerate ads and slow sites "functioning as intended" than the much-less-frequent but far-more-maddening broken functionality that takes me "longer than it should" to troublehsoot.

I'm not sure I've used uBlock though, mostly ABP over the years.