Yeah, I think a lot of this can be attributed to institutional and infrastructural inertia, abstraction debt, second+-order ignorance, and narrowing of specialty. People now building these things are probably good enough at React etc. to do stuff that needs to be done with it almost anywhere, but their focus needs to be ML.

The people that could make terminal stuff super fast at low level are retired on an island, dead, or don't have the other specialties required by companies like this, and users don't care as much about 16.7ms on a terminal when the thing is building their app 10x faster so the trade off is obvious.