imho having a more accessible contribution workflow would increase the number of people interested in spending time in reviewing.

Regardless of the many problems of web forges today the ability to review only what's changed between the various revisions of a pull request and the comments in a single view is not achievable with a simple email workflow. You end up reimplementing the PR/MR functionality with other tools, exactly as is happening with the Guix QA tools. I love them but we're reimplementing gitlab/gitea/codeberg by parsing patch revisions from emails subjects.