One of the other problems is they used the current monorails to do all the testing for the automation. They wanted to lock that in and incorporate it into the new version. 10 years ago it wasn't ready. Even 5 years ago it wasn't ready. Part of the reason the monorails are so ridiculously overdue is because the automation was done on Disney time. And then they tried to squeeze the investment a little longer, and now the 50th is coming up and they can't afford to have the monorails down, and only crappy Bombardier is really willing to work with their ancient beams and tech, and it's a bloody mess. So they decided to try and refurb one more time, sinking money into that, and pushing off a revamp that gets messier all the time because the beams and infrastructure are incompatible with modern standards.
Frankly the monorail is a disaster. A disaster Disney created, exacerbated by outside factors for sure, but created by Disney. And there is no good way out. It will be fascinating to see how WDW eventually undoes this Gordian Knot. Given how iconic the monorail is, and the way it ties together the 7 Seas Resorts, it's hard to see them scrapping it even if it does make economic sense. But, there is almost no good way of keeping it without dropping several monorail loads of gold bars.