See and that's where I believe you are conflating things. Guest satisfaction as quantitatively measured by Disney can only go so high. That is certainly correct. If guest satisfaction, on a quantitative scale, is already high for Everest then there isn't any way Disney can improve the attraction which will result in significantly higher guest satisfaction scores. Because guest satisfaction would already be (almost) as high as Disney is willing to measure it.
However actual guest satisfaction— that is, the enjoyment guests get out of an experience —does not 'only go so far.' There are always means by which Disney can improve its attractions that will result in guests enjoying them more. Bringing back the yeti is an example of that. Plussing BTMR is another. So instead of asking this question,
one could more aptly ask guests to compare to the two versions of the attraction. Let's say we could hypothetically sit guests down to ride EE with and without the yeti show scene, and then ask them which version they preferred. If they preferred the attraction with the giant yeti AA, then the yeti necessarily improves guest satisfaction of the ride. If guests said they liked both versions and that the yeti didn't really do that much for them, then that would mean the yeti wouldn't improve guest satisfaction and bringing it back would have no benefit for the park.
I however am 100% banking on the former. Remember, EE as a coaster actually ain't all that. It's fun, but it's no Steel Vengeance or VelociCoaster. The ride system isn't that special and no one needs to spend thousands of dollars or travel thousands of miles to go on what is essentially a middling rollercoaster. I got CP 2+ hours away. What brings Disney over the top is its theming. That includes EE. The yeti was THE headlining themed/story moment of the attraction. Losing it means losing one of the main 'wow moments' of the ride. Bringing it back means wowing guests more than they are being wowed currently.
bad show is a missed opportunity for good show. Good show equals higher attraction quality. Higher attraction quality equals a more enjoyable experience for guests. No yeti on EE is a glaring example of this.