I feel like this is why monetizing the fast passes will leave such a bad taste in the mouths of many. I think we're all perfectly happy to fork over more money for new experiences or perks. We'll say "heck yeah, I'll save extra money to pay for a custom lightsaber or a dessert party or a new tour or extra morning hours at a park or a special event" because we feel like we're paying for something that is above and beyond what's included in our resort and/or park tickets. But after years of free fast passes, when you slap a price on them people then look at what they are getting for their ever-increasing resort & park ticket prices and think "What the heck Disney? You're charging more but giving me less." Because really, even when they add new lands and new attractions, many people probably already feel like they are paying more to enter the park and more to stay on property due to those new things. They don't necessarily see them as added value to what they've already been paying. And now if they feel they need a fast pass in order to actually experience the new things that the increased prices have funded, it feels like they're double-dipping into our pockets for the same experience.
People will still go, but if people go in with a subdued love for the park, they may not have as good a time, and they may not opt to come back as often, or at all. And then if there is a recession or something that lowers the crowd in the future, will Disney be able to get some of those people back? i don't know. They can try making those things free again, but at least some people are going to scoff at that ploy.