I'm not saying this to be snooty or whatever, but RSI is also solvable via a custom keyboard or learning Vim motions (or both). I had really bad RSI and it totally went away after the combo of learning to type properly (which you mentioned in your post) and switching to Vim full time. Vim motions reduce the amount of stretching you need to do by a LOT. Snippets also helped. I am of course talking about in The Before Times.
I am saying this to be a little snooty. Your take is very dismissive to a large group of people whose experiences you don't know. I agree that split/custom keyboards and vim are awesome; I have used them for 25 years. But the idea that you can reduce RSI treatment and everyone's situation to something so simple just isn't true. It is fine to recommend solutions to people who are suffering, but to dismiss their problems as being "solved" comes across as basically calling them stupid for not helping themselves.
I know you didn't say that, and you softened your language, but many people with disabilities or chronic conditions have to deal with everyone they share their problems with telling them their "cure". Its exhausting.