Making MK a neglected park doesn't solve its issues. MK provides a vastly subpar experience compared to Disneyland, for example.
None of the parks are sufficiently built up.
This is a bit of an either/or, when that's not the reality.
Making the other parks slightly less neglected isn't solving anything.
In an ideal world, they should all get expansion alongside each other. Currently, MK has 29 rides, HS 9, AK 8, and Epcot 12. If MK, AK, Epcot, and HS all grew at the same rate, once Magic Kingdom equals Disneyland's 39 rides, HS would have 19, AK 18, and Epcot 22.
My biggest complaint currently with Tokyo DisneySea is a lack of rides. They're adding four through Fantasy Springs, bringing its total number up to 24.
My point, is all these parks have a long way to go, so wishing expansion away from Magic Kingdom doesn't make much sense. Arguably, Hollywood Studios and Animal Kingdom need it more, but regardless, it's not MK that doesn't.
It seems MK and AK are getting the expansion they need. Who knows about HS.