Anecdotally, at work I usually contribute to 2 codebases. The first, we've invested into optimizing CI heavily, CI is generally not flakey and almost always takes less than 10 mins to run. It's also engineered to generally fail early most of the time, so if it's going to break, you often find out in < 2mins.
The other codebase takes about 20mins, often takes >15mins to fail and is generally quite flakey.
Subjectively speaking, the code quality on the first codebase is much higher, since making those small changes is generally quite painless.