STOP reading the FP+ posts on this board.
If you insist on reading them, be selective.
Most reports I've read from people who have actually USED FP+ are generally positive.
There are things they like about it, there are things they don't like. But, isn't that like anything else in the world?
Back away from the Theme Parks board and have a great time on your trip!!!
Then you are being "Selective" in your reading... Even people who are very "Pro" FP+ are now grasping and saying the reason the negative FP+ reviews, reviews not speculation, are so numerous is because people are more likely to complain then to write how awesome something was/is. The negative reviews very much outweigh the positive.
Fast passes are basically just a way that you KNOW you get the ride the 3 rides you love the most, without standing in line (more than a few minutes generally).
Well, not really, in MK maybe, but with tiers in the other 3 parks, not at all. Unless you don't plan on riding any Tier 1 rides I guess.
But for the overall consensus, I would generally agree, you can still enjoy Disney, in fact many of the negative FP+ reviews have said they still had a good or great time, but they just don't like FP. Many of them have said they will not return until there are changes to FP, but many of them will continue to return as well.
Disney is still a great place, no doubt, and you can have a great time. But, if you sit down, and recognize that its not worth the cost for you, No one should blame you. For a lot of people, who are concerned with doing rides/attractions, FP+ is a major downgrade. If rides are your thing, if they are the prime reason you go to WDW, I could very much see you cancelling, if they are only part of a mix of things you like, I wouldn't worry as much about it, though you might decide afterwards that you might take a break, or not return to Disney .... I am sure you will enjoy this trip.