nah, git was absolutely the right thing to squat on - its ubiquitous, so making it seamlessly powerful and easy to use makes for easy adoption. If it was built on pijul or whatever, I'd never have given it a try.

to the extent that niche things might not be supported (yet), so be it. It suits the needs of the vast majority of people. Moreover, if you need those things, I BET you can just do it via git and then carry on working in jj, since jj sits on top of git