When I started dabbling in web development, writing HTML and CSS was already its own job, and professional JavaScript developers basically did not exist. This was before TypeScript, before Node, before Ajax, before React or even jQuery. If anything has exploded in complexity in the intervening years, it's the JavaScript part of the equation.

I agree that it's increasingly silly to ask someone to be an expert in all of frontend. But the primary driver of that is not all the new CSS features we're getting.