It took me more time to pre-plan our FP+ than the act of getting a legacy FP in the parks over the course of a full day ever took.
As I have said repeatedly - we did attractions by land. We'd pull a FP, do everything else in the land, then "go back". That was not a big time suck. It took less time than pre-planning FP+ did - for *us*.
TBH, that isn't really debatable - this is my personal experience I'm talking about. Your experience is different, I get it. but that doesn't mean my experience was the same as yours.
I respect that you are being honest about your experience, so please respect that I am being honest in describing mine.
Oddly we did much more criss-crossing the parks on the last trip than ever, due to the need to use the Kiosks to see whats available and book anything beyond the first 3.
We used to, as I said, just tour and pick up as we went along. Now sure this sometimes meant a backtrack here and there, or it might have meant a diversion to swing by a ride on the way to another (not really altering our path very much.) It resulted in things like walking from Splash to BTMRR to grab and FP then back to splash to ride ... then to BTRMM to ride with the FP. Or Popping over to space, Grabbing and FP then riding Buzz or Astro or People mover, then popping back to space, I will fully admit in Epcot it often involved heading to TT to grab an FP then over to Soarin to ride, but we would work our way back to TT riding along the way to use the FP. And Epcot was FAR better with FP- than it is with FP+ in our experience.
Anyway, we found our group doing much more criss-crossing. Because we would get to the kiosk and take what was available. For one instance we were at Splash, headed to the kiosk in the tunnel at the entrance of Frontier land, picked up Big Thunder, Back to big thunder, back to the kiosk, FP for Space, Across to Space, Spaced, Kiosk near Stitch, then over to Peter Pan.
Now, we didn't -have- to do this, but Kiosks still require you to crisscross the parks, and in my experience (and most peoples from what I see here) have longer waits than FP- (sometimes significant waits) ... So beyond the 3, I really don't see the advantage in FP+ over FP- ...
This then really brings the debate down to whether having 3 pre-booked (and the planning/scheduling and potentially feeling like you are scheduled that this involves), subject to tiers and availability, potentially needing to rework all this as you go if your plans/itinerary changes, and longer SB wait times for a significant portion of the attractions --- is better for you than ---- having a true clean slate each day, with equal access to all the FPs, lower SB wait times for a significant number of attractions, without having to do as much preplanning/scheduling or worrying about availability if your plans change.
This will impact different people different ways, depending on style and what you enjoy.
For us, the advantage to FP+ was on arrival day. Because we had stuff booked that afternoon/evening. That was nice, not that we wouldn't have been able to pull FPs under FP-, but with such a short period in the park and on our first day, it was good to know we could have it all set up ... beyond that, FP+ lost all its advantages for us. They just don't work for us, they are offset be the negative impacts it had on our trip.