1. The only things that WebPKI CAs are required to attest to is that domain validation was properly completed and that the private key is not compromised. The system is designed (in both intent and practice) for any website to be able to easily get a certificate, and even the most untrustworthy, undesirable websites can and do get certificates on the regular. In contrast, Google's remote attestation proposal is clearly intended to assess the trustworthiness/desirability of the client.
2. The TLS requirement imposes a burden on website operators but provides a clear benefit for end users, which is totally in line with the Internet's Priority of Constituencies[1]. In contrast, Google's attestation proposal places a burden on end uses for the benefit of website operators, which violates the Priority of Constituencies.
Additionally, I must note that Firefox also requires a TLS certificate for HTTP/3 (as they did for HTTP/2). Not sure why you'd omit Mozilla from your list of browser makers doing this, but it's a misrepresentation to imply that this is something only "mega-corp browsers" do, when there is actually broad agreement that this is a good thing.
But this only becomes a serious problem when HTTP/1.1 support is removed. Mozilla will never remove HTTP/1.1 support from Firefox. Google/Microsoft/Apple are chomping at the bit to remove HTTP/1.1 from their products.