You don’t always need to replace the part with something the manufacturer offers as a replacement. Something like a screen board might be hard/ impossible to find an alternative for, but things like buttons or sensors inside of mice are rarely something made specifically by the mouse manufacturer. They can almost always be replaced by an equivalent generic part. Hell, my 3D printer motherboard took a shit on me a couple years ago, and I bought an aftermarket board and installed 3rd party firmware on it to get it up and running again.

Like you said it’d be great if it were just easy for everyone to do these things, but as devices get more advanced they’re gonna require more advanced knowledge to work on, and not everyone has the time, interest, or resources to learn how to diagnose and repair stuff.