There's no question that, at best, Thanksgiving week runs a distant 4th in terms of crowd levels behind the three holidays you mention. Depending on how spring breaks line up, I wouldn't be surprised if there are other weeks in February to April that are more crowded.
It's why I thought Thanksgiving would be the first good test of FP+. All onsite resorts are using FP+ and crowds are up but not at peak. From what I observed, it's clear that they have some problems to work out, all of which are solvable.
However, looking at the big picture, it's also clear that FP+ simply changes how wait times are distributed. Some guests will be better off with FP+, some will be worse.
In total, FP+ doesn't improve anything, it only changes it. FP+ & MDE feel like a lot of smoke-and-mirrors, as if we are supposed to equate "different" with "better".
I suspect the new DAS policy is having a bigger impact than FP+ on wait times. And that new policy was effected at modest cost.
At least when increased crowds are attracted by brick-and-mortar additions, they are partially offset by increased ride capacity. Not with MyMagic+ though.
Given that the stated goal of MyMagic+ is to get guests to stay onsite longer and since MyMagic+ doesn't increase attraction capacity, a successful MyMagic+ program simply means that we all wait in line longer.
Guest opinions are influenced largely by how long they wait in lines. If MyMagic+ does keep guests onsite longer, then MyMagic+ essentially was designed to make guests less happy.
MyMagic+ only could have been approved by executives who spend half their days with their heads buried in their smart phones, who have never stood in hour-long Standby lines like everyone else.