You've said in both one and three that they are "loud", so really we can lump reasons one and three together. And to be frank, you've said nearly the same thing in reasons two and three, so instead let's clear the clutter and see what you're saying:
1. It's loud and obnoxious
2. It ruins the build-up of the ride by showing the ghosts to be friendly before they're supposed to be revealed as such rather than keeping the sense of foreboding prior to entering the HM.
3. It's poorly designed, only slightly better than a McDonalds' playground
Reasons one and three are, to me, not valid reasons to show why the new HM queue is bad. Those are individual value judgments based on the opinion of YOU. Simply because you think the queue is loud, obnoxious, and poorly designed does not actually make them so. I personally don't find the HM queue loud, obnoxious, or poorly designed - so who is right? Me? You? Hence why neither reason can be considered - they're too subjective.
The second reason has a bit more weight and can be considered. One thing to keep in mind is that the Imagineers could never truly come to a consensus between the HM being scary or funny because the person who could break the tie, Walt, had died. Which is why the HM has both elements within it. The other thing to keep in mind is the location of the HM - the Magic Kingdom. While I personally love things that are quite scary, the reputation that the Magic Kingdom has is for family-style rides and attractions. Nothing too fast, nothing too scary. Do we need to re-hash the entire fiasco with Alien Encounter to show what happens when something *really* scary is put into the Magic Kingdom? An attraction called "The Haunted Mansion" already has a built-in scary factor into it - a musical organ and some moving books are not going to take that away. And if it can re-assure some smaller younger guests that the HM isn't terrifying (just slightly creepy, IMO) and get them to experience it, I'm all for it.