The "bottleneck" model of performance has limitations.

There are a lot of systems where useless work and other inefficiencies are spread all over the place. Even though I think garbage collection is underrated (e.g. Rustifarians will agree with me in 15 years) it's a good example because of the nonlocality that profilers miss or misunderstand.

You can make great prop bets around "I'll rewrite your Array-of-Structures code to Structure-of-Arrays code and it will get much faster"

https://en.wikipedia.org/wiki/AoS_and_SoA

because SoA usually is much more cache friendly and AoS makes the memory hierarchy perform poorly in a way profilers can't see. The more time somebody spends looking at profilers and more they quote Rule 1 the more they get blindsided by it.