The problem right now is the lines are not short. Granted, some of that is social distancing, but for my trip starting last week, many guests weren’t being so good with the distancing anyway and were much closer behind me than even the three feet now recommended. Also, since the queues are overflowing into areas where queues weren’t planned, there is very little relief from the sun. If the lines were short, and moving, I would agree with you, but that was not my experience the past couple weeks.
I went to WDW for years before FP, and in fact, never used paper FP because of all the extra backtracking (getting the pass and then returning to ride). I remember how efficient the lines used to be before FP. However, there were fewer people overall in the parks as well. The experience of waiting in line now is nothing like waiting in line then. I don’t recall ever waiting an hour for a ride back then, and it’s too long to be waiting for a ride now. Yes, not every attraction has an hour wait, but I personally did see waits as high as 80 minutes last week at varying times, and this isn’t even the summer rush yet.
I don’t know that FP+ will come back, or if something else will take it’s place, but they need to get the lines under control before they increase capacity.