This assumes that nobody will learn "the old stuff" and only focus on the new stuff. I don't think that's how it works, otherwise we wouldn't see PHP in the wil

This assumes that nobody will learn "the old stuff" and only focus on the new stuff. I don't think that's how it works, otherwise we wouldn't see PHP in the wild anymore. Or anything else that's more than five years old. On the other hand, people are integrating libraries for ANYTHING in their projects and don't care about that either. Call me old-fashioned, but PHP + MySQL with HTML, CSS and a handful of jQuery has still brought me everywhere in terms of tech stack. Maybe I'm just doing shitty jobs, I don't know, but it works and the client is happy, so it doesn't look like a problem for me.