My opinion is that going back to normal mode is too important a key to be a key combo, and a weird one at that (is it [ or ] ?). I am pretty sure you can get used to it but we humans get used to anything really, doesn't make it good. My pressing on CapsLock happens at a subconscious level. Quick edit and then punctuate with CapsLock with the pinkie. Some random key combo is not acceptable.

But again my point is that the default sucks. You probably learned a about Ctrl + [ while looking online for alternatives after realizing the default sucked

at least on linux you can map caps lock to esc if tapped and ctrl if held