Earlier quoted context omitted.
This is the job of your operating system's scheduler - to divide the limited resource of your computer's CPU time among different competing tasks. In the modern era, a program cannot take more than its fair share of CPU time - otherwise, a runaway program could easily render your computer nearly unusable. (Linux, macOS and Windows all use preemptive multitasking.) The way to tell your operating system what you desire…
I'm well aware of that. I also know that, in general, having to schedule things slows them down. If everything I'm running is trying to schedule something on my entire machine, it is giving my OS more work. Which will, by necessity, be harder to schedule and slow things down. I'm not necessarily against all of this, but I'm also not eagerly embracing more crap to slow down my machine for no apparent reason.
I could almost guarantee you this is not the bottleneck of any modern setup.