I'm a multirepo advocate, but I suggest splits similarly.

Maybe it's my old-timey way of releasing software, but because I do releases as RPMs, it bothers me less if you do things like have your base library, your backend services, and your frontend in the same repo. If they need to be able to be deployed independently, I just split them up as subpackages.

I guess most language package managers don't really have such a concept, so people are optimizing for that...