A small change that will not cost them will be the park hopping time rule. Immediately make some happiness without expense.
That would pretty much make the park reservation system obsolete.
No, it wouldn't, at least not at WDW. Very few people these days spring for the extra hopping option, except for AP holders, and they have considerably thinned out that herd at this point. Inflation will contribute as well, as more people try to maximize their vacation dollars.
The thing is, Disney AP holders (esp. WDW) are VERY vocal. They talk a lot, and reporters find what they say and go fishing for stories. Making them a wee bit happier can only help the situation. (The one exception to that is the eBay merch resellers. Those people have to be stopped, not because I feel they are taking unfair advantage to my detriment, but because they make mgmt. predisposed to throw out the baby with the bathwater. Disney doesn't like losing on those merchandise exclusives, and the easiest way to quell them is to eliminate APs, but it's overkill. A company with as much big data at their fingertips as WDW can easily find and ban these people, all it would take is a decision to take a hard line.)
Did you notice the other day that notice that walk-up day pass buyers no longer need a reservation? They say that they will tell them which parks are available and not sell those that are not, but I do not believe for a hot minute that someone standing at the MK ticket booth will be told that their only choice for that day is DAK. I'm betting any money that they will be let in to whatever park they are standing at the gate of unless the park is truly maxxed out, such as on Easter or Xmas.
FWIW, I would be completely satisfied with changing down the reservation system to still require reservations on major attendance days but not every day, and I think the average AP holder would be fine with that idea.
Iger is in a golden position right now to pull back on some of the pandemic changes and tweak things, because even though they were planned on his previous watch, in practice there is a LOT of room for improvement. He can vaguely blame the problems on Chapek, and thus has a lot more wiggle room than would otherwise be there.
I think what sealed Chapek's fate is his tendency to target people he perceived as threats, and to give outsize power to people he perceived as loyal to him personally. That creates institutional paranoia, and take it from me; once that sets in, a company is in deep, deep trouble. The 2d tier execs read the writing on the wall and acted.