Also, all the functions that are already in the standard library but are made in a way that don't use more modern features:

- Functions that use map-like and set-like objects instead of maps and sets.

- Functions that should be async that aren't

- Async functions that should be cancellable, but aren't

- Functions that should use the disposable and async disposable stack (e.g. the `using` keyword)

- Functions that should return deeply immutable data structures but can't. (The R̶e̶c̶o̶r̶d̶s̶ ̶a̶n̶d̶ ̶T̶u̶p̶l̶e̶s̶ / Composites, and Structs proposals would help here)

- Concurrency coordination primitives (Imagine an array of 10 async functions that we wish to run. Going through them one at a time is too slow. `Promise.allSettled()` executes them all at the same time which might slow things down even more due to bottlenecking. We should have an easy way to say only execute a maximum of 3 at a time. As 1 function resolves, the next one is started, until all are resolved).