> Having build and push as part of the same job is frustrating and I view it as a sign that a CI system is built with the expectation of having everything happen post commit by shoveling money into a CI auto-scaler

No, the idea is to build and push images you can test directly afterwards in the same conditions. With cache and such, build times shouldn't be too long

Gitlab CI just runs shell commands, it's pretty trivial to pull the same image its using in the job, and run the same commands locally.

If you have long CI times, that can hinder development productivity and should be improved as much as possible, or a local replica of the CI needs to be created.