> There can only be a couple thousand threads at the same time.

You can easily have tens of thousands of threads on Linux. Beyond 50 000 or so you may need to adjust some settings using `sysctl`, but after that you should be able to push things much further.

Task counts themselves are also a pretty useless metric. Sure, you can have may fibers doing nothing. But once they start doing something, that may no longer be the case (this of course depends on the workload).

> Threads are really hard to work with - race conditions everywhere. Async doesn't have this.

You can still have race conditions in async code, as race conditions aren't limited to just parallel operations.