You may be interested in a project that's doing almost exactly that: a new content type that sits alongside the "classic" web, with a heavy focus on performance and only JavaScript from a vetted repository allowed.
What downsides does AMP have that your proposal would not?
Another way to think about this is, people were already thinking along these lines and tried to build something, and that thing is AMP. If you want to build something that avoids the failings you see in AMP, you're going to need to think hard about how your plan is different.
Those are mostly not the case anymore for AMP; the only one that looks correct to me is that AMP documents have to include the AMP runtime. If you wanted to make a pure HTML+CSS page, with no JavaScript, I can't think of any technical reason why the AMP specification couldn't be extended to consider that valid AMP. I think the main question is whether there are many sites that would be interested in serving that way?
* AMP is not specific to mobile, though it did start that way; there are sites that serve all of their pages in AMP format to both mobile and desktop users.
(Disclosure: I work for Google, speaking only for myself)
> If you wanted to make a pure HTML+CSS page, with no JavaScript, I can't think of any technical reason why the AMP specification couldn't be extended to consider that valid AMP.
> Meaning that right now it isn't that way, right?
Correct, the current spec doesn't allow that. But, as I said, I think that is something that could reasonably easily change if many sites wanted to publish with vanilla CSS and HTML.
> For some reason everyone still seems to associate amp with Google, and the only times I can remember finding AMP pages are when I search with Google
https://amp.dev/