It's really not bad:

    <picture>
    <source srcset="image.webp" type="image/webp" />
    <img src="image.jpg">
    </picture>

and you only need to bother with this on images it might matter (e.g. key large multi MB photos in a blog post or something not all of the 20x20 logo icons that would be less than 2kb even if uncompressed).

nothing about web for the last decade has been about no-JS HTML

its an option but doesn't leave you anything to contribute. the web is fragmented most of the toolchain is for simplifying deployment into that fragmented place without caring that it is fragmented. so not really nuts when everything already takes care of it for you. you can stick with no-JS HTML cached on an edge node just as well, or not cached if you expect low traffic, its whatever.