I think modern phone processors, as limited as they are, could be pretty fast at rendering classic HTML and CSS. I know we want more from our webpages now, but the rendering as a static image is part of what makes AMP feel so weird and not like a normal webpage.
It’s not a static image. It gets rendered into an iframe they swap in, which is only possible because they control the html rendered given the constraints of the amp format.
HN for example loads quite fast on mobile. I don’t think there is anything about client-rendered HTML and CSS that can’t be adequately fast even on fairly restricted clients.
Of course you can slow things down with advanced features, my point was that a google-led test for certified “Fast Webpages” that get promoted in search results could have most of the positive impacts of AMP without the strange complexities.