Big big problem with the oly 4/3 were tiny viewfinders. Was not just sensor tech at the time.
FF high ISO performance in low light is what I'm after for shooting my kids sports in dim gyms and night football games. Probably silly reason for most but its a very valid reason for someone wanting ff.
I'm totally with you on crop cameras being perfectly suitable for most anything else. Ken Rockwell is right about all anyone needing is a d3100.
One other thing you may not be considering. With light gathering of a modern ff sensor most could get by with much smaller light and cheaper f4 lenses rather than having to spend the price of a car for big 2.8 zooms.
I agree with most of your points