The only part of the Earthly pitch that resonated with me was the ability to run the CI locally. When debugging your CI, it is just faster to find problems when you can run on your own box.

I have a gnarly GitHub Actions script that took forever to get right because the debug cycle was 10 minutes long.

I feel you on that one. There is also Act (https://github.com/nektos/act) and Dagger.io.