You could write a translation or compatibility layer for web content that reduces it to your minimal version.

But then no one bothers implementing your document format because their existing HTML already works and it's not worth investing more time into such a small userbase, and then you're maintaining even more code

That's not necessarily true. Markdown is a good example of compile-to-html format that has gained huge popularity.

As a transitive format. There are no places full of Markdown documents to read and share, where Markdown is the final display format. It's all translated to HTML.

If you did write a "markdown over http" spec and implemented a browser for it, it would be about 15 seconds before someone reimplemeted it as a JS library.

In fact, if I was trying to build "markdown over http" I'd start with the JS library. Skip the native browser application entirely.

One problem with markdown is it's technically a superset not a subset of HTML. You can put a canvas and video that's in it. It's not a great standalone format

MDX !== markdown

With any of this, isn’t it a, “build it and they will come,” situation?

Web Assembly, for example, is pretty pointless if browsers don’t support it. Browsers now support it, so it can be used, and that’s slowly happening.

It seems like the new document standard would need to be written, the benefits would need to be demonstrated, to the point support is integrated into the mainstream browsers, and then people who see benefit from the (I assume) easier/faster/better development, can start using it for new projects or integrating it into existing projects.

Trying to make an entirely new internet based on a new document standard would be rough. At this point, I don’t see that as a way forward, unless it brings something extremely compelling that users want and go crazy for, which can’t be duplicated with existing technology. I’m thinking Napster levels of hype and consumer desire.