> When I've wanted a "container," I've used a real VM.

I mean, sure, that's great for you. Maybe you've just never visited a block where you can't reasonably use a VM to replace containers, such as a good amount of shops where local environments approximate production (i.e. containers).

> I just installed Docker desktop last week

All I can say is, "good luck!" DD is by far the worst container runtime for MacOS.