I disagree. In a world of different architectures, out-of-order execution, asymmetric cores, branch prediction, per-core caching and information leakage between threads and the branch not taken, my opinion is firmly that most people shouldn't be writing multithreaded code because it is almost impossible to get it correct and safe.

The effects can be subtle and lurk for years until a seemingly unrelated change exposes them. It starts with optimizations like instead of spawning a thread, you use a thread pool, possibly abstracted as some kind of executor service. Other code might use different thread pools to isolate them because each pool has its own limits on the number of threads. Some might grow but usually they won't.

Until one day you end up with thread starvation and a deadlock through a series of benign seeming optimizations. There are threads around but not in the right pools and the entire thing grinds to a halt.

Cooperative async/await on a single thread is the ideal solution for most use cases, particularly with complete environment teardown between requests. Yes, this is basically the PHP model.