I think there would have been backlash from people no matter what they did, simply because they replaced Splash, the frequently-noted favorite attraction of several people on every side of this board, many other boards, and many people who casually visited the parks.
I really don't think it's a reach to make such a statement. If they redid Haunted Mansion tomorrow and replaced it with, I don't know, a take on the Family Madrigal house from Encanto utilizing the exact same infrastructure, there's basically nothing they could do for it to live up to HM for me, because Haunted Mansion is my favorite ride. If I can straight up admit to such hypothetical scenarios, than I'm unsure why many people are unable to do so with this *actual* scenario.
Perhaps a book report version would have been better received, but I still don't see a world where a book report TBA is received super well either because of what it replaced. I know I didn't imagine that period where book report attractions were widely derided and seen as lazy. If you personally thought differently, perhaps you were an exception to that, but it was a very real sentiment in the community for a long time.
Now maybe this ride really is garbage or close to it, as seems to be the consensus, but let's be honest, this (not meaning this forum or this website in this instance, but arguably the entire Disney theme park fan community, NOR do I mean this in anything other than a strictly objective and neutral fashion) is a very biased group of people that have certain things they like or don't like, and certain things that are/were sacred cows, both in terms of big things and small. Is there really a chance that most people were truly going to come in to this particular ride neutral? The Splashers were always going to be (at the very least) resentful because it replaced an iconic attraction; likewise, there were others excited about the prospect of a PATF ride that they were going to love this no matter what. From where I'm sitting, this is all very clear and self-evident. If people disagree with me, oh well.