I would argue that the guest experience is more likely to be enhanced if attendance is capped at the highest demand parks, and crowds are intentionally balanced across all destinations.
Coercing people to purchase less desirable products by rationing the ones they really want to buy is a bad strategy.
It almost reminds one of how things used to work in the Soviet Union. Everyone wanted to buy nice stuff, but nice stuff was scarce. So people waited in long lines, or did whatever they had to do to get their hands on it. If they couldn't, they were forced to make do with the not so nice alternatives.
Part of those demand imbalances were due to incompetence of the people in charge. They didn't make enough of what people wanted, and they didn't price things appropriately. But the state had a monopoly, so those people kept their jobs (until they didn't...)
We've got the same problems here: it's not "our" fault that demand for Magic Kingdom and Animal Kingdom don't match their respective capacities. That's Disney's fault. But Disney wants to cram one down our throats while withholding the other. Disney can do that because they are a monopoly (somewhat.) But it doesn't make it a good strategy, any more than it did when central planners did it in "non-market economies."
How do market economies solve imbalances in supply and demand? They don't typically use rationing. That tends to piss people off. They try to increase demand of less desirable products by improving them in the long run, while using pricing to adjust demand in the short run.
How would pricing work in this context? Crowding is kind of a cost and it also affects desirability. You could give people a fixed number of credits they could use to purchase visits, and make some parks more "expensive." You could give people a certain number of free Fastpasses per year per park, and maybe give more for the parks you want them to visit more. You could make Annual pass discounts more generous in some parks than others.
But by far the best way to solve this is to make all of the parks desirability match their capacity. By adding more and better rides and attractions to the less desirable parks. And if Disney hasn't been able to do that, that's on them, not us. They need to fix this.