Comment by pornel

GitLab doesn't have an equivalent of GitHub actions (except an alpha-quality prototype).

GitHub Actions can share runtime environment, which makes them cheap to compose. GitLab components are separately launched Docker containers, which makes them heavyweight and unsuitable for small things (e.g. a CI component can't install a dependency or set configuration for your build, because your build won't be running there).

The components aren't even actual components. They're just YAML templates concatenated with other YAML that appends lines to a bash script. This means you can't write smart integrations that refer to things like "the output path of the Build component", because there's no such entity. It's just some bash with some env var.