I think this can only happen if there are viable alternatives.
For instance, the UI at setups such as https://git.devuan.org/Daemonratte/gtk2-ng is quite ok-ish, in my opinion. Granted, it is mostly copy/paste from github but that still is about 1000000x better than sourceforge's interface - and gitlab's UI too (I just hate gitlab's UI, they seem to love complexity and a billion features only 0.000001% ever need; GitHub, with all its faults, is for the most part really simple - not everywhere, e. g. GitHub wiki setup sucks, but by and large I think it is simple overall).
Github definitely has the better UI but if it weren't for network effects I'd be pushing to migrate to Gitlab pretty hard.
Gitlab’s UI is extremely terrible. It’s hard to even explain how bad it is.
Once you get used to it, it's not so bad which is probably true for all functional UIs. I switch between gitlab and GitHub quite a lot and I can't say which one is objectively better. I do like that cross-linking is easier in GitHub but I prefer gitlab ci over GitHub actions. Too bad that gitlab ci runner has removed the command to run ci locally but third party foss solutions are there.
If replacing github wholesale isn't viable, how does the story for replacing GitHub Actions look like currently? I don't remember the pre-Github-Actions days of everyone using CircleCI with a github integration in a negative light. I've noticed that since then a couple of CI providers have sprung up that differentiate themselves with faster build speeds, but I haven't really kept up with that market
I've been thinking of reverting back to Circle CI.