I'd say the limitations are relative to your use case: `docker build` works well enough in most cases, but sometimes it's not the right tool for the job (e.g., you cannot use `docker build` inside an AWS Lambda, you can get way better performance from specialized tools in some cases [1], etc)

[1]: see my sibling comment at https://news.ycombinator.com/item?id=48301041

Creating multi arch builds for starters. Maybe creating image from just composing layers instead of “running” a Dockerfile? The first I find cumbersome and is easily overcome by using buildx.

I haven’t tried lately, but I think running a build still requires running a docker engine. Buildx has builders that run as containers.