Yeah - and as a result of that, the builds I do for .NET in GitHub Actions are an order of magnitude quicker to run than the previous pipelines I had in GitLab,

Yeah - and as a result of that, the builds I do for .NET in GitHub Actions are an order of magnitude quicker to run than the previous pipelines I had in GitLab, where everything was painfully slow because it all ran inside Docker. I get the point about it not being ideal for self-hosted runners, not having ephemeral storage etc. But I disagree that the hosted GitHub Actions runners don't provide a good experience. If your build needs it - e.g. you're building something to deploy to your K8s cluster, use your Dockerfile and build in Docker. If you just want to compile some code, what's the point?