All the more reason why they should be sliced and diced into oblivion.
just add a new git remote and push. less so for issues and and pulls, but at least your dev team/ci doesn't end up blocked.
The engineers who build the early versions were folks at the top of their field, and compensated accordingly. Those folks have long since moved on, and the whole thing is maintained by a mix of newcomers and whichever old hands didn't manage to promote out, while the PMs shuffle the UX to justify everyones salary...