Yup. I’ve worked with some really great software engineers in the gaming industry, and they don’t have a fucking clue how to optimize a game, and it’s because optimizing the game doesn’t take a clue. It takes legwork, and diagnostics, and digging, and digging, and digging.
It’s never what you think, because if it was, it would have been fixed already.
We shipped well optimized games, and we did so because the games were (relatively) small, and our engineers were absolute pro sleuths.