All good points. Maybe having worked a lot with concurrent and distributed system makes me distrustful of relying on unit/integration tests for correctness; I've seen too many concurrency issues pass CI validation. But unit tests also sometimes miss edge cases in more straightforward code, so I'm still a bit more cautious.

I also agree that merge requests should be short and understandable in 10 minutes, but IME this happy state often does not obtain in practice. It shouldn't, but it often does, whether it's mission creep, whether it's turning out that a change is more complex than originally imagined, or whether it is unavoidably complex and cannot be broken down further.