I can only guess at what we would have done. Minus a crappy year, I know we would have been LESS likely to have cancelled, but my hunch is that we would have cancelled anyway. We aren't "soak up the atmosphere, grab some dinner and enjoy being off work" people at WDW. If I want atmosphere, good food and a break from normal life, I'm going to Paris. We are early in/late out, ride, ride, ride people at WDW. We pull 6-8 FP a day and know how to work a park to maximize what we can do.
We have found that with careful planning, we can do every attraction we want to do (we usually skip Stitch, Captain EO, Tiki Room and a few others) at least once and many 3-6 times. Yes, that is in a lower crowd season. We really don't lounge by the pool....I can do that in Texas for most of the year. Sometimes, we do CS only so as to maximize ride time. As I said, we vacation hard. But WDW was never stressful, just busy.
I could deal with booking ADRs, as I always had great luck booking what I wanted. But booking FP+, especially with tiers, is not a good fit for us. And I don't want to have to haul a phone around, checking on/changing things. I don't want to be in a park full of people who do. With us on FP+ and our friends (whom we were meeting some days) on regular FP, coordinating rides together was looking to be too dang hard.
The way we travel, we hit a low crowd park and may even change that park last minute if the crowd predictor changes. We get there early, start pulling FP, and ride anything in the area that has a short standby time. The second we can pull another FP, we do. Rinse, repeat. We usually work a park in zones. Our most glorious day was when we got to MK for early entry and managed 9 or 10 rides the first 90 minutes. They were just walk on, really. Now granted, most were just short kiddie rides, but still amazing. Wonderful morning.
Unless it is the slowest day ever, I do not see FP+ allowing us our normal 6-8 EE, 4-6 RnR and ToT and even 2-3 TSMM, with 1-2 times on most other attractions. That means we'll get to do much less of what makes us most happy. I think
Disneyland may well be a better fit for us now and I am sure Universal is.
It's 100% WDW's right to change, but it's in our best interest to be aware of whether or not those changes are a good fit for our individual family. And these changes don't work well for us. If someone still wants to go, I wish them a fantastic time. I want them to have a great trip and feel it was money well spent. These changes will work well for some and even great for others. A large percentage of first timers will never form an opinion, as it will be all they know. And WDW will keep on going just fine.
I realize some posters are convinced these FP+ changes are not a valid reason for THEM to change their vacation, but how close minded does a person (not necessarily you) have to be to be unable to fathom that the changes ARE a valid reason for others to cancel? Do they really think everyone vacations, acts, thinks, feels the same way they do? Or that at a minimum, they should? If so, they should try wrapping their head around the fact that some people wouldn't go to WDW for free.
So while I cannot say 100% whether we would have cancelled if we'd had a good year, I am pretty darn certain we would have.