Well said about constructive criticism. I think the main thing people overlook is the base problem that MM+ is attempting to solve.
Survey's of park guests overwhelmingly show that families (particularly families new to going to WDW) are frightened of having to send a runner to get FastPasses, check on dining, and figure out a place from which they can see a parade. The sheer size and unfamiliarity of the parks makes the act of separating, going on a quest, and reuniting seem like an unpleasant adventure.
MM+ is an attempt to smooth out this process and take the success of FastPass to a new level.
There are those that lament the invention of FastPass and long for the "Good ol'Days", but I rarely read posts that talk about the fantastic time that was had in a 90 minute queue for Splash Mountain.
I agree that for first time visitors, the immensity of the parks can be a bit daunting. And a lot of families don't like separating to get FPs and the hassle to find good parade seats, etc. Sometimes as veteran Disney goers, you lose touch of how it was to be a newbie, since you know all the secrets and the parks like the back of your hand.
Though while FP has been a success, I think it has been a greater success to those who can, so to speak, "work the system" Those people who know exactly when and where to get FPs, and use maybe 5 or 6 a day, at multiple parks. I think now though, FP+ is taking that advantage away. Now someone who was great with the old system, now is limited to 3 a day in one park. It hampers park hopping and reduces the number of FPs per day. As a first timer, I can see how making all your reservations weeks in advance can potentially make your vacation less hectic. However for a veteran, annual passholder, this really cramps the ability to simply go into the parks for a day. FPs for Soarin might have been out a week ago, and now you're going to have to stand in a long line.
While you are correct I didn't hear anyone talking about the fantastic times they had waiting in 90 min lines at Splash Mountain, I didn't remember any complaints either. I think that was because the line was in continuous motion. What makes lines artificially longer today is the FP system, and the lines sometimes seem to never move, because FPs are being received at the front. I think FP+, increasing the amount of FP stations throughout the parks, will only increase this issue. The 3 rides you get a FP+ for will be great, however the rides that you don't have FPs for probably will have longer lines. And those 3 FP+ you get may not be for the rides you want, at the times you want, unless of course you reserve them 60 days in advance.
For some reason I don't have an issue with making ADRs months in advance. But for some reason, forcing me to choose what time I want to do 3 attractions per day 2 months ahead of time seems like our vacation is becoming too constrained. And of course we could choose to not make AFPs, but then we run the risk of them selling out and waiting hours for rides that we could have gotten a FP for. It just seems to go in a circle, at least in my view.