just to expand - the 20% was what I was told Disney expected the take-up rate of Genie+ to be, or more specifically, what IT was told to anticipate the take-up rate to be, but it would up being 40-50%.
I was told second hand so definitely could be in correct but wouldn't be the first time Disney underestimated demand and I do think they thought use of it would be easy and less stressful but it go so heavily used by people trying to maximize it (which makes sense when you spend $ on it) that it didn't work as intended.
Now, they went to their first line of defense in those cases which is to raise the price of it to try and reduce demand but so many Disney guest got trained by FP+ that using a line skipping is what you need to do in order to have a good trip (which ties into a more general shift in society, and then Disney feeds into it and it snowballs).
But I wouldn't be surprised if Disney would like a system that a smaller % of guests use but rather than rip the bandaid and just go right to something like only Premier Pass they are trying to have their cake and eat it too