It doesn't seem like a particularly bad approach. I would guess that most developers don't have the skills (or time, for that matter) to be able to efficiently

It doesn't seem like a particularly bad approach. I would guess that most developers don't have the skills (or time, for that matter) to be able to efficiently write code at the hand optimisation level. Abstracting this away to the compiler is a safe bet, and developers will soon learn ways to at least generally optimise the code for the compiler, much like people have already learned to optimise code for javac, v8, etc.