WHATWG wants to co-mingle document rendering with javascript (this is the real reason they are removing XSLT and not proposing a replacement, it skirts this enforcement) so that when you try to disable javascript or block tracking it breaks the document rendering, leaving the only option to leave Javascript enabled and ad blockers off. Other protocols gemini, gopher etc don’t have the same issues because they’re already excluding Javascript.
What is really needed is a hard fork of major browsers by a grass roots community to advance HTML standards to include partial template rendering solutions without the reliance on Javascript.
Of course this is a startup forum so the response is just going to be wittled down to observations about economic value. However if users start to change/fight then the economics will too.
It wouldn't be that weird a thought for me that, preferably a group of, nation states cough up some serious money and give this a real start, beginning, and end in the form of a stable release. This already happens with major science and space projects, with budgets of billions. A browser is not simply a bunch'a software, having a modular open browser is a major deal and benefit to society at this point. Perhaps arguably more valuable than pumping yet more energy in a particle accelerator and other of mankind's pet projects in search for the unknown unknowns and deal with more pressing known knowns first.