The statement was a little strong, but in my experience it contains some truth. People who has never used a lower-level programming language can't often recognize these performance issues.
I've often found the opposite; people who use C get excited about using >> rather than / because it saved a few cycles on very old compilers, but fail to notice where they could've made it a million times faster by using a hash table rather than a linked list.
Unless a senior developer / a "wise" developer reviews the artifact created and allows him/herself to state:
"This is not effective code. Refactor it by x y z".
The problem is, I think, this is NOT happening or at least to seldom because it "does not pay off", because "the aws boxes are sooo cheap!"
I'd say: the aws boxes are way too cheap and effectively misused. What should have been a way to scale up apps with reasonable effort turned into an energy and resources burning landfill. Granted, at least it is a shared landfill which really helps with from the resources/energy point of view.
(Juniors) Coders should be able to power the machines by driving a bicycle ergometer ... as a way to make the homo-sapience grasp the effects of their "mental work" ;)