Wow, lots to address here.
1. Before the pandemic, Iger recognized that guest enjoyment of the parks were measurably lower (GSATS) when it was overcrowded. That hurt the brand. People can't pay for overpriced meals if all the restaurants are already full. They're just standing there trying to find food at QS's that don't have a 30 minute line. They leave, and they don't come back. This hurts "the brand" and "the brand" is Disney's most valuable asset. It makes people pay extra not only for really good services and goods... but they'll also give Disney a pass and pay extra for stuff that's only 'meh.'
2. So, Disney had been looking for ways to reduce peak attendance and bring in more people to the 'off times' so that the parks would be constantly and comfortably full for maximum profit.
3. So, Disney kept raising prices while offering discounts to the dead-times, to even out the highs and lows. The holiday parties in the Fall were to entice more people to those previous dead times, and that worked tremendously.
4. And yet, park overcrowding still happened, especially at MK. They were a victim of their own success. And so, let's make this clear: IT WASN'T WORKING PERFECTLY LIKE YOU CLAIM IT WAS. At least, not in the past decade. Millions more people were crowding into WDW year after year and it seemed no matter how much Disney jacked up the prices way above inflation and the cost of living, more and more people attended WDW every year. This is what happens when anyone with a ticket or AP can show up whenever they want, and they all show up on the same weekend and holiday days creating a very unpleasant overcrowding situation. It wasn't working.
5. Park reservations was the obvious answer, but, it was also the nuclear option, since guests would hate the restrictions it imposed. Something which I kept on saying on these forums for years before the pandemic.
6. When the pandemic hit, do you remember "six foot distancing"? You can't let the usual 50,000 people enter the MK and maintain six foot distancing. On top of that, the governments weren't letting large entertainment venues operate at full capacity and limited them to just 10% or 25% or 50% of normal. But, when Disney sells "any time tickets" and has tons of AP holders, how do they limit attendance? With park reservations. The pandemic pretty much forced them to limit capacity.
7. So, how do you limit capacity? Well, on Christmas or New Years Day, you can just turn people away at the tapstile and tell them you're full because there's an hour line to use the restrooms, like WDW has done in the past. (See, it didn't always work in the past). Or, you can make people make reservations so you never get to that level of attendance that overwhelms the facilities and your staffing.
8. So, yes, park reservations, which was always an option, but a nuclear one, was the only real solution, due to severe capacity reductions imposed by the pandemic.
9. And yes, of course they're keeping it. And I understand the hate for it. I struggled with it on my visits in December and May. But, it's the only solution that will work to keep capacity from overwhelming staffing (and there is still a labor shortage despite some peoples' disbelief). The only other solution is to keep raising prices dramatically until they find the tipping point at which people won't pay... and apparently, it's much, much higher than anyone thought it would be.
I understand you want to go the MK anytime you want. But so do 21 million other people. And letting them all chose whatever day they want is just crazy. There will be days that just too many show up. What do you do, let in 90,000 people into the MK to live in 2 hour long lines and scrambling to find something to eat in 40 minute lines?
[And yes, Disney's fault for not increasing capacity, but what if consumer demand constantly outstripped increased capacity?]
