Not at all my experience. I’ve often tried things like telling Claude this SIMD code I wrote performed poorly and I needed some ideas to make it go faster. Claude usually does a good job rewriting the SIMD to use different and faster operations.
I'm not a C++ programmer, but wouldn't your example be a fairly structured problem? You wanted to improve performance of a specific part of your code base.
That sounds like a pretty "structured" problem to me.