Before just throwing that out there I would encourage you to spend some time walking through how it would actually work. Do't just touch on the 35,000 foot view of where stations and routes would be, focus on how the guest would actually get from place to place using that system. What would a guest have to go through to get from point to point? What would happen when a train arrives at a park at park close and it's full and nobody can board (there would be a riot) because the park before it on the beam closed around the same time. How many stops and changes does it take go get from all the common point A to PoInt B scenarios? How long would it take a guest to get between the farthest points of the routes vs what it takes today (do this without hyperbole I the measurements).
Its easy to throw things like that out there but it's vital that you clearly understand exactly how the guests would actually experience this. In most cases, history has taught me that the guest experience would be so confusing, difficult and slow that the value is just not there. While it may seem like it would be cool, it would not likely be a positive experience for the guests.
Of course this is speculation. Its all a moot point anyways. I am not doing a thesis on this. This is clearly not a "Give me proof" style discussion. The point was - if the effort went into the monorail, instead of other transport enhancements, I believe it is something that could have been done, and disprove the rumor that it was always too expensive to do.
But I do disagree with your impression of guest experience. Being consistent knowing a monorail can take you to all parks is valuable. Not sure how having a clean monorail loop would be any more confusing that looking for bus terminals, schedules, vans, or driving.