I'd settle for an restricted subset of HTML only as a light standard. Tables and bold and h-tags and stuff are fine, it's CSS and Javascript that slow everything down for (on ordinary pages) basically no benefit. Reserve boxes for images but click/tap to fetch and show. Make always-show an option I guess. Videos are well-marked links that open in some other program. Let the user set some colors and sizes for basic text elements and call it a day. 99% of the web would be better for the user in such a restricted format and we could stop spending so much money peacocking up plain ol' websites.
If you remove HTML, you have more or less Gopher [1].
Maybe add back a subset of markdown to have a few semantic marks and ease navigation. Tables should be treated as what they are, that is formatted data that specialized software for viewing (it took way too long for HTML makers to realize that showing static tables that you can't sort or filter is only good at layout control).
You mean something like text/enriched? It was designed in the mid-90s to be something like HTML-lite for people who thought HTML (that is, HTML 2.0, not HTML5) was too feature-rich to be used for email. It also never took off.
It's not. Really. Lower contrast, crowded lines and skinny fonts aren't making things better. FOUC isn't making things better. The larger file(s) required to achieve worse results isn't making things better.
