They don't have as much wiggle room when it comes to WDW. It's already over 100 dollars on the gate entrance fee for Magic Kingdom. Asking people to then fork out for Fast Pass too wont go down well and you need Fast Pass in WDW like no other place in the world.
Disneyland Paris isn't much cheaper. One day undated tickets are £90 which is comparable to the $119ish for the WDW parks. Although Paris seems to be more often £62 a day if you are choosing specific days, but at WDW most people buy 5+ days of tickets which also brings the price down a long way. All the three western Disney parks are fairly comparable in price really with California being most expensive.
I would actually think that California would have the worst reaction to any removal as they are still operating the original style FP with a small option to pay to book on the app (instead of going to the ride entrance).
Whereas at WDW they already have FP+ where you had to book 60 (for on site guests) or 30 (for everyone else) days in advance, so they had moved to a different system where on site guests had a big advantage. Given therefore many WDW guests got used to paying more to stay on site and for additional early entry or late night parties etc its probably easier to sell it to the vacation guests.
Disneyland has a lot more locals and passholders.