Many times I have suggested this idea on HN. Always gets shot down. Perhaps the problem is that such a move toward simplicity is perceieved as benefitting users more than web developers.

There are certainly folks at hosting providers and similar service companies who advocate using different browsers for different purposes, e.g., for security reasons. For example, it makes little sense to use the same program to browse random sites on the web as you do to log in to your bank's website. However there are more reasons that just "security" (namely performance, IMO). If "security" is the only reason one would use a different program, then people just point to "sandboxing" and use one browser for everything.

As for paring down HTML, isn't that sort of what Firefox "Reader" mode or AMP does? If you try viewing some AMP urls in links text-only browser, they look particularly good, and the news site "paywalls" do not work. I have been using text-only browser and other, smaller programs to perform text retrieval from the web for many years and they work very well, much better than the gigantic omnibus everything-in-one programs supplied by the ad tech corporations.

Thus, the responses that claim "It would never work" make little sense to me because in my case it has already worked for decades. I doubt I am the only user who values speed and simplicity.