The killer is that everything that works for individuals trying to get through the day and make the web a bit smoother is immediately used by industrial crawlers strip mining the Internet, and you can't block one without blocking the other. A future where the web is only accessible via device attestation is extremely dystopian but so is an Internet where every drop of content goes into an LLM training set.
Things like this is why all of the worthwhile content is going to drain into balkanized spaces, and we're all the poorer for it.
I am not saying that forks like this are a good idea, but I have enough frustration with said techniques that I sympathize with the effort.
Also, patched browsers have existed since long ago, although they were not open-source.