It is not true of all projects _to the same degree_. Highly conventional, opinionated systems have a higher learning curve but yield a more consistent result given developers with inconsistent skill levels and investment in architectural design of an application.

That is a fancy way to say: React gets new devs productive fast, and so it has tons of them available for work, but that comes at the cost of producing more spaghetti that more experienced devs inevitably have to clean up.