> If the compile is long because the implementation is poor, that needs to be fixed
The compile time could be long because the implementation is poor. But it's also possible that the specific requirements do not allow for a significantly faster compile time.
That's why the requirements matter. They determine the space of possible implementations. If the requirements eliminate all "fast" implementations, then the resulting user experience will be poor because of slow compile times.
The best example of this problem is probably SPARK, a variant of Ada which permits formal verification.
Its verifiers are awfully finicky, and tuning the parameters (including selecting the most appropriate verifier) can mean the difference between successful completion in a few seconds, and outright non-termination/timeout-with-failure.
It's true that the answer is to have better verifiers, but that's not just a matter of tweaking the verifier code, it's a serious research challenge. One of the most serious problems with formal methods is the ability to scale.
The compile time could be long because the implementation is poor. But it's also possible that the specific requirements do not allow for a significantly faster compile time.
That's why the requirements matter. They determine the space of possible implementations. If the requirements eliminate all "fast" implementations, then the resulting user experience will be poor because of slow compile times.