It's funny you said "shower-thinking" because showers are one of the few places where it's not practical to use a device and you really are alone with your thoughts. A normal day to day activity that is the same sort of "stare at walls" state that the OP describes.
Yeah we moved on from SVN to git because SVN branches were truly a pain in the ass to work with. I truly do not have any rough edges or big pains in my day to day git workflow.
I'll field this one as someone who has used regular ol' Vim for ~18 years and never switched. Why switch if your tool is working fine? I use vim literally every day all day long and it does everything I need it to do. Switching has a cost and there's no reason to pay it if it's working fine.