CI that isn't running on your servers wants very deep understanding of how your process works so they can minimize their costs (this is true whether or not you pay for using CI)
Totally! It's a legitimate thing! I just wish that I had more tools for dynamically providing this information to CI so that it could work better but I could also write relatively general tooling with a general purpose language.
The ideal for me is (this is very silly and glib and a total category error) LSP but for CI. Tooling that is relatively normalized, letting me (for example) have a pytest plugin that "does sharding" cleanly across multiple CI operators.
There's some stuff and conventions already of course, but in particular caching and spinning up jobs dynamically are still not there.
