No site is an island. Even if I keep my own website's implementation minimal I still end up interacting with the rest of the internet via web pages with less minimal markup.

However, if you also had a like-minded community of similarly minimal websites, a mechanism to minify websites, search engines that prioritized minimal (or minifiable) websites, and a social convention of avoiding linking to any website unless it was minimal (or minifiable) then you'd end up with something like the Gemini community.

In fact, I suspect something like that will supplant Gemini in practice. Browsers already have reader modes and some search engines allow you to block certain domains. I could easily imagine search engines or browsers providing greater end-user control over this sort of thing in the future.