Task management is not multitasking ... nor is all multitasking the same
There is task-switching (which is what tablet OSes do - and what Windows did prior to Windows 95).
There is cooperative multitasking (which is what MacOS 9 and earlier, and Windows 95 thru ME did).
And there is pre-emptive multitasking, which is what UNIX and Linux have done almost since the beginning.
The demands of the latter are what make desktop operating systems "bloated".