The unsolved part: reliable, automated setup that works across the long tail of repos without human intervention. Docker helps but doesn't solve it (many repos don't have working Dockerfiles, and building those is itself a setup problem).
but dockerfile is not the complete setup you need to configure a lot of other things, and in a lot of cases dockerfile is not even getting generated correctly, try out gitpod they generate devcontainer.json which is a standard format across different platforms, but generating a devcontainer.json or Dockerfile has never been easy for agents specially when the repositories are complex.