alt Hacker News1. This isn't true whatsoever. You can easily do better than std::vector (trivial relocation support, non-inlined grow), better than C# List<T> (ref T accessor, batch add API, maybe even an add-uninitialised API or in-place constructing specific things), better than a Python list (this one is obvious), etc.
2. This is a better point but depending on your workload, I don't think this is unheard of. Or at the very least, if your workload is simple, you can grab one off the top of the benchmarks, point AI at it to customise it a bit then you're good. But to be fair this one's a bigger structural investment so I do see your point. For smaller utilities the tradeoff is pretty clear.
Is it obvious? Those existing APIs have known performance characteristics and deep integration into several other libraries. The moment you custom-roll your own root library, you break integration with all existing other libraries that depend on the defaults. To add, your LLM has to think about your new custom version rather than looking at the billions of lines of examples using the one it already knows works from decades of historical data.
If you really, really need some ultra-micro-optimization, you’re obviously not the target of this; but unless you’re doing HFT or the most inner loop of a game engine, the standard library and all its deep integration and battle-testedness is worth the 1% perf hit.