My contradictory proof: I have been working on an old service with tons of performance issues, from server memory bloat, client graph rendering, excessive network requests, excessive repeat rendering, memory leaks, resource leaks, etc.

The app and service are measurably and subjectively faster. Because I chose to have the LLM focus on solving those problems. It obviously can. It described the issues in big-O.

It is a priority problem, as it always has been, not a knowledge or skill problem, like it always has been.