I’m sure that’s a factor, however we need to probably also acknowledge that “younger people” (whether developers or managers or etc) lack exposure to things that were genuinely better previously (and where technology is concerned there are many examples), and thus have no mental model for it. They literally don’t know any better, and they’re operating within that framework.

Crude oversimplification: if all you’ve ever known are slow and bloated web app UIs on mobile phones, you’re simply not going to know how to make good design/development choices outside that environment.