With the Fast Pass system properly utilized, I would maybe sit through 3 or 4 standby lines all day and the rest of the day would be character meet and greets, play areas, table service meals, parades, shows, fireworks, and actual rides (usually around 10-12 of them without waits due to proper use of the Fast Pass system). Currently, there are no character meet and greets and the kids play areas are all closed. There are no parades, no shows, no fireworks, and table service menus are restricted and some of the best of them are not open, and in any case sit down meals eat up too much of the day during the decreased park hours. So right now, there's almost literally nothing to do but ride the rides and therefore it's not much of a problem that you're standing in line more of the day. Right now, Disney reminds me of what it used to be like when I was a punky teenager in the late 80s - a race to do as many rollercoaster rides as possible with definite benefits to going on weekdays. This has been neat for a change, but once you ride "the mountains", or Slinky Dog, or FoP like 5 times in a row just because you can, it gets old.
So once all the other stuff opens up again, I think people are going to be wishing they had their Fast Passes back and that they could be doing all other more "magical" stuff while waiting for rides instead of standing in line, even if it's just a whole bunch of shorter lines than before.
That said, I doubt that they ever bring Fast Passes back again. They were already doing visitor surveys asking questions about how to revamp or eliminate the Fast Pass system even before the shutdown, and currently cast members have been instructed to refer to the entrances signed "Fast Pass" as "alternative entrances" or something like that, which to me sounds like they are trying to phase out the term. I think the writing is on the wall that they intend to move to some sort of virtual queue system, but we'll have to wait to see how it will be implemented.