You might want to check out GNAP. I did an overview of it here: https://fusionauth.io/blog/2021/01/07/gnap-next-gen-oauth/ but you can also check out the spec here: https://datatracker.ietf.org/doc/draft-ietf-gnap-core-protoc...

They are aware of the issues of the browser centricity of OAuth.

It's definitely not the simpler protocol you describe, but it's one way to look at the future.