Comment by IshKebab
Yeah I think this is totally true. The trouble is there are loads of build systems and loads of platforms that want to provide CI with different features and capabilities. It's difficult to connect them.
One workaround that I have briefly played with but haven't tried in anger: Gitlab lets you dynamically create its `.gitlab-ci.yaml` file: https://docs.gitlab.com/ci/pipelines/downstream_pipelines/#d...
So you can have your build system construct its DAG and then convert that into a `.gitlab-ci.yaml` to run the actual commands (which may be on different platforms, machines, etc.). Haven't tried it though.
I've used dynamic pipelines. They work quite well, with two caveats: now your build process is two step and slower. And there are implementation bugs on Gitlab's side: https://gitlab.com/groups/gitlab-org/-/epics/8205
FWIW Github also allows creating CI definitions dynamically.