My favourite thing about the command key is the position - it’s way further to the right than ctrl on most keyboards, which means you don’t have to contort your thumb back and apply lateral pressure to your thumb joint when copy-pasting.
I’m either doing it wrong on Windows or the entire world is putting up with unnecessary finger pain because whoever chose Ctrl-C was a masochist.
Originally, the Ctrl key was to the left of A, where Caps Lock is now. This makes most Ctrl key shortcuts a lot more comfortable. They moved Ctrl to the bottom left with the Model M keyboard, which became the standard modern PC keyboard layout. As far as I can tell, the justification for this was that it made the layout more familiar to typewriter users, since Caps Lock is in the same position it's in on a typewriter (see https://bitsavers.org/pdf/ibm/pc/IBM_Personal_Computer_Semin... page 24). Personally, I always remap my key layout on every PC I use so left Ctrl is swapped with Caps Lock.
I'm not sure what hand position you're using, but on the keyboard I'm at right now, I put my left little finger on control, and use my left index finger for the c/v. Do you mean that you're using your thumb for control and index for c/v?
I’m either doing it wrong on Windows or the entire world is putting up with unnecessary finger pain because whoever chose Ctrl-C was a masochist.