Simple answer that could be answered by anyone who has worked Mansion/Pirates/Small World/ect since Fastpass was shoehorned in:
If everyone doesn't get fastpasses and fastpass is a paid service, you have much less people in the Fastpass line.
If there are less people in the fastpass line, the standby line rarely stops moving.
If the standby line rarely stops moving, the standby wait is shorter.
Yeet.
I am a former CM as well (I am guessing you are from your name.)
This only works if some of the people in your plan decide not to ride.
It would work, EXCEPT rides have capacities. Which you know, as that is why we are having this discussion. BUT, you forget this with your argument's proof. You also forget that "Having less people in the FP queue" means that they are now MORE people in the regular/standby/non-FP queue, unless some give up.
Let me ask you.
When you go to a restaurant without a reservation and they tell you the wait is 2hrs, do you think you would have gotten a table quicker if there were no reservation system and people just had to wait in a line?
Now, you could say "yes" because a lot of people would give up. To which you might be right, BUT the people that had to wait in line for 1.5 hours wouldn't be as happy as if they could have PLANNED and made a reservation and walked in and been seated in 10-15 minutes.
ALSO, the restaurant would not make as much money, because rather than having its customers drop a dime on a drink during the 10-15 minutes they are waiting for their reservation to be seated, the customer is standing in a line and getting upset, not having fun and not getting a drink or an appetizer while having their short wait.
In short (too late):
- FP+ allows you to plan a good time
- It means you don't have to run all over the park to try and secure your FPs
- The "Good old days" were not as good and there are many factors that impact wait times (to this point, you mention PotC and the FP before and after. BUT you don't take into account the rise in popularity due to the movies and the impact that has on the ride's wait time.)
Now FP needs to continue to improve. They need to allow for park hopping and they could move it up to 3 in the first half of the day and 2-3 at night, that would be nice. And maybe as they add attractions they will have the capacity to do this (although WDW will probably be more popular, and that will mean more capacity will be needed if we want an expansion.)
I hesitate to point out that restaurants in EPCOT used to only have SAME DAY reservations, now we are out to 6 months. If anything with FP+ they should sync this up with when you make restaurant reservations, as it is tough now to have to pick where you are eating but not know if you will have any rides to do in the park you've chosen.