There's much ridiculous hatred for OS threads based on people's biases of operating systems and hardware from 20 years ago.

So much so that they'll sign themselves up for async frameworks that thread steal at will and bounce things all over cores causing cache line bouncing and associated memory stalls, not understanding what this is doing to their performance profile.

And endure complexity, etc. through awkward async call chains and function colouring.

Most people's applications would be totally fine just spawning OS threads and using them without fear and dropping into a futex when waiting on I/O; or using the kernel's own async completion frameworks. The OS scheduler is highly efficient, and it is very good at managing multiple cores and even being aware asymmetrical CPU hierarchies, etc.. Likely more efficient than half the async runtimes out there.

hardware from 10 years ago - do you have benchmarks for more recent hardware?

https://vorner.github.io/async-bench.html