Because the LLMs were trained on average software which doesn't give a shit about performance and they'll revert to the mean for sufficiently complicated projects. While they can help with searching for performance improvements, they also are liable to cheat if you aren't reviewing them for correctness of any algorithmic changes. Also you need to be responsible for teaching them the right benchmarks to use, since, again, performance optimization has been niche and not the standard.
As someone who programmed in Rust since before 1.0 (I started by reading the github issues daily in college when that was still feasible, volume-wise) and worked professionally using it, it can’t write better Rust than I can yet.
Save for one area, which is mostly because it was annoying to write and check with miri, which is unsafe code. It can loop through testing edge cases at my direction quickly.
But it can write code better than the average programmer without doubt. It’s only at the edge you can tell the places where it suffers. It has improved a lot, though. That rate of progress doesn’t guarantee it will capture all of that remaining edge but it’s still impressive.
That's the one silver lining. I've always kept a lean desktop of mostly terminal based programs, and I've heard one too many times "just buy more RAM" as a defense for resource intensive graphical programs using Electron or modern browsers in general.
