Disney doesn't have to provide the best possible experience (as if that could be quantified), and never has. They just need to give you something that you value more than the cash you're willing to trade for it.
Disney is not a sports franchise, and it's fans are not analogous. The commitment level for a sports fan in terms of time and treasure are relatively small, and the vast majority of fans interact with the team in ways that don't require a direct financial exchange.
I've been a Bengals fan since expansion, and I've been to exactly 2 games (Playoff and AFC championship) and have never bought a jersey. I've been a Buckeye fan since birth and have only been to one game but our basement is a shrine of memorabilia.
Disney's customers will demonstrate that what's good for Disney is not good for them when they stop coming. There is no other measure.
You wrote:
For anything to be good for Disney, it has to be good for Disney's customers. The aren't selling fuel, groceries or medicine.
Then that they don't have to give you the best experience, just enough that you are willing to part with your cash for it ...
Therefore you original premise is false.
It is quite possible that Disney can do something good for Disney, and Bad for its guests, so long as they continue to come back. It can still be bad for the guests, like cutting back on the snacks on the dining plan. That's no way good for the guest, but its good for Disney, but it isn't enough to make me stop going.
And your description of sports fans is hilarious, and completely based on your own lack of dedication to a sports team. The fans between Disney and Sports teams are quite analogous.
While YOU might not invest much in your sports teams, many of my friends spend more on their sports teams every year than we spend on our family vacation to Disney every year. Millions of people do this, every year.
The NFL, alone, is aiming to bring in $25 Billion per year over the next few years.
People invest a ton of time and treasure into their sports teams, even when the don't win, when they don't seem to get much return on their investment. The same could very well be true of Disney. I have even heard as much here on the boards. Basically, "Disney is our thing" so we keep going, despite the fact that the quality or value of their vacation has been diminished.