Well, "loved" is not the word I would use. It's an improvement over the chaos before, where everyone used some other bespoke tool to build their BSPs. Yocto at least is some kind of standard now, but not a particularly good one (granted, it's a really difficult problem to solve). I don't know anyone actually enjoying working with Yocto.

Yocto is also hated for its unnessesary complexity in embedded software circles.