It is well known that general purpose operating systems do not allow real time applications. The reason is people prefer an OS that can do a lot of things well

It is well known that general purpose operating systems do not allow real time applications. The reason is people prefer an OS that can do a lot of things well enough, vs a system that can do one thing in real time. Real time OS's exist, and you would never want to build a desktop environment on them. Also, the OS will never become the bottleneck for any general purpose software because you'll never have a team of programmers good enough to make it so. All the performance issues be due to mistakes in the application itself.