> Usually poorly.

On the contrary. You can focus exactly on the features the higher level game code needs. The C++ stdlib is (for the most part) poorly designed, usually poorly implemented, the main reason for slow build times, and its complexity explodes because it needs to consider all edge cases that most code bases don't ever trigger.

A specialized dynamic array class in a few hundred lines (at most!) and with just the required features is much more useful than the 20kloc monster that's pulled in with `#include <vector>` and which doesn't even do bounds checking in the 'idiomatic' usage.

some of the STL is easy to improve on. For example, std::unordered_map performs poorly due to pointer stability requirements in the standard. Most performance sensitive C++ codebases will use something like abseil's hash maps instead.

Which is worse? std's mess or one you control? I'd take any random game engine's STL over std any day.

C+ Standard Template Library is the best designed part of C++ library. It was designed by Alexander Stepanov.

https://en.wikipedia.org/wiki/Alexander_Stepanov