I asked Google Bard whether it thought Web Environment Integrity was a good or bad idea. Surprisingly, not only did it respond that it was a bad idea, it even went on to urge Google to drop the proposal.
Internet is just a series of tubes. You're talking about alternative content/services providers (news, video, shopping, etc.) if the existing ones choose to require only approved browsers.
It would be more feasible to fork the Web rather than the Internet. The Web is all software and protocols, while the Internet would require different physical service providers.
I don't think it's pedantic. It's relevant. Web is a mess, thanks largely to Google. But we still have a lot of other protocols and the freedom to come up with new alternatives. If they figure out how to abuse the TCP/IP stack, then it's game over. We might as well start from scratch.