I used to have a JS-free site, and even though it had background animations, they could all be done with clever CSS. Unfortunately I wanted these animations to persist as the user clicked around the site, so that they could grow in complexity or interesting-ness over time, instead of resetting. This is not possible without a JS framework to turn the site into an SPA, so I switched the other way, from eleventy to gastby.
JavaScript frameworks don’t exist to provide user demanded features but to provide developer demanded capabilities. Since frameworks exist solely to supplement the developer no site really needs a framework and sites benefit universally from not having one.