> the huge majority of software engineers are not aware of almost any transformations that an optimizing compiler does

They may not, but they can be. Buy a book like "Engineering a Compiler", familiarize yourself with the Optimization chapters, study some papers and the compiler source code (most are OSS). Optimization techniques are not spell locked in a cave under a mountain waiting for the chosen one.

We can always verify the compiler that way, but it's costly. Instead, we trust the developers just like we trust that the restaurant's chef are not poisoning our food.