It's an opinion, how can it not be valid? Because it differs from your opinion?
I've used Mac OS for quite a bit more than 20 minutes, although in fairness I have to admit that it was Mac OS 1 thru 7 so it's not very fair to compare it to modern Windows computers.
I never did like CP/M, but I have a pretty good feel for MS-DOS.
Every now and then I drag an old Kaypro luggable out of the basement and play with CP/M, just to remind myself how bad it is