Gee thanks.
I like to have my right hand on a mouse or trackpad, so two handed chords are much less convenient.
Macs manage to make one-handed chords for copy and paste ergonomic, but on a PC it's user error?
Cmd-C is not any more ergonomic than Ctrl-C. You are only speaking from position of habit. Pressing modifier with tucked in thumb is not great for it.
If someone is concerned about ergonomics, they should buy ergonomic keyboard. Standard layouts are crap.
Decades is an exaggeration. It was less than a decade after Digital started using Control-C as a process interrupt in their PDP-10 operating systems (1967) to when Mr Tesler devised his mapping to a copy operation (1974-1976) for Smalltalk-76, and only four years after C was born. CP/M is the much more likely source of widespread usage of control-C as an interrupt, and it was contemporaneous (1974) with Tesler’s mapping.