MacBook Pro (early 2011) Cpu (i5 2415m) working on minimum operating frequency (800 mhz on 99 % load)

Try an SMC reset and PRAM reset (hold the PRAM reset for at least three chimes so it activates several times).

Try running the Apple Hardware Test.

If the system is not getting enough power, then it can run at very low levels even under load. Verify the laptop's power adapter is working correctly. Maybe the battery is failing so even if the power adapter is good, the battery might keep the system from having enough power. Check the battery status by Option clicking on the battery icon in the menu bar. Anything but "Normal" or "Good" indicates the battery should be replaced.

I am not aware of any similar program.

Does the same thing happen in Safe Mode?

You could try reinstalling macOS on top of itself or even perform an erase and clean install using Recovery Mode (Command + R) or Internet Recovery Mode using Command + Option + R.

Some 15" & 17" 2011 models had known GPU issues. I wonder if the GPU may be interfering somehow. Maybe you could force the laptop to use the Intel GPU instead of the discrete GPU. I know an app exists to force the Intel GPU to be used instead, but I don't have the links or information. There are a number of posts on these forums with links and directions.