GP didnt say that. They said lot of devs become "front end" or "back end" specialists which means that they cannot do full stack. Full stack devs knowing React is fine. The problem is that most "React devs" don't know full stack and most "backend devs" don't know full stack.
Why does being a front end or back end specialist mean you can’t do full stack? If I’m a full stack dev that’s a back end specialist I can still write a complete feature myself just fine, thank you very much. But of course, if I’m having trouble with some part on the front end I might ask a front end specialist colleague for help, and vice versa.
