Your second paragraph disproves your first. Websites' needs didn't drastically increase (I'm ignoring nonsense like WebGPU; render graphics outside the web browser like a God-fearing Christian!), but their complexity did. Why? Well, we told everyone with a pulse they could make six figures "doing web development", and we're reaping what we've sown.
You can still design websites like it's 2005, and they'll be damn fast. But pitch something like MFC or even PHP to a 20-something frontend developer now and watch the blood drain from their face.
"We" build both. You might be building WebApps, I certianly don't and so are countless others. The web is not one homogenous thing where everyone is doing the same thing at the same time.
Different people work on different projects serving different needs and we have to acknowledge that otherwise we end up in these silly tech-religious arguments where people think there's one and only one way to do things and that's certianly not the case.
You can still design websites like it's 2005, and they'll be damn fast. But pitch something like MFC or even PHP to a 20-something frontend developer now and watch the blood drain from their face.