Let's not forget, also, that for about ten years if not longer, the common consensus was that Wicked was not only a bad musical, it was THE BAD MUSICAL, whose badness and whose impact on the theatrical culture at large was actively harmful. It was very much treated the way rock and roll is treated in Bye Bye Birdie, as a stylistically retrograde and zombifying entity that was dragging other new musicals down with it and harming the tastes and brains of the people who encountered it. That cheese-touch was passed to Heathers, which has not entirely shaken it off despite twelve years of extreme success.
I think the relative disappointment (critical more than audience or financial) of Part 2 is making people look back at Part 1 more critically. You're going to see some thinkpieces like "wait... did Wicked suck all along?," and former darlings Erivo and Grande are going to be caricatured and lampooned a lot harder than they were before.
Now, a moderate sophomore slump is nothing in terms of "two enormously successful projects," but when the eyes of the entire world are on it this way, I wonder if this could have a dampening effect on musical movies to come, or on the reputations as theatre performers of Erivo and Grande. It's not another Dr. Dolittle, for sure, but... with Hollywood the way it is, do we know it won't be TREATED as one?