Non-developers/designers were able to do a lot of the frontend stuff. With the "new" complexity of frontend development that's mostly gone.
I've seen it a few times with my own eyes that in teams the 1-5 frontenders specialised in html/css had a really hard time switching to react, at the same time more seasoned developers felt like fish in the water.
Considering the scarcity of developers that's actual a big deal, more work for developers while at the same time less work for traditional frontenders.