It's not about hours of planning. Since, as you pointed out, it's not like you were picking at time for each like movie theater tickets. It was about having 3 fixed points in time months before your trip with no thoughts to the weather, how you're feeling, or anything that may have changed in the last two months. If you were going to spend the entire day in the park (which many here probably do), then it may not have mattered as much. But, if you do days split across many activities, multiple parks, throw in some resort time or a water park, like to adjust based on the weather as some parks are more fun than others in the rain or heat. Or, maybe you've got an EPCOT dinner every night. Then, those 3 fixed points established months in advance can feel restrictive and controlling.
We used to do fast passes the day before mostly. Which was clearly not the power user process, but was less stressful for us.
Planners clearly liked the pre selection part of FP+ significantly. Others, not so much.
The park pass system should be taken to a farm up state and never return.
Side note: There is quite literally no shade at all between SW:SGE and Toy Story land. I swear they teamed up with the weather and tried to kill us last week.
We went to DHS an extra day ANYWAY because it's where our reservation was. A reservation made in case we didn't get RotR the first time. We did, at the forced rope drop, followed by SR and TS. A LL for MMRR and SDD. The only ride missed the first day was Muppets. So, at least we did that on the second reservation day when we had to tap in before going anywhere else.