Keep in mind the river diversion works out to approximately 13.5% of its former length. Somewhere between 1/7th - 1/8th. It's not really SWL that is diverting the river, it's the Fantasmic show building that is taking up the added space. Moving from the island to backstage. The Railroad is being quite diverted though, primarily for SWL. As an aside, don't forget Big Thunder Mountain in terms of significant upheaval to Walt's Park in a stones throw of the areas we are currently discussing.
Something I've come to realize is for a lot of people it is the motivation behind the change rather than the change itself. Park promotion of formerly non-Disney acquisitions, mandates to create whole lands on single franchises, a shift to expensive immersion in franchised environments. The use of the parks to hawk merchandise, bump exec pays. The drive to appease share holders, franchise fans, the common denominator general public or the board. The shift to lavish environments with guest highways rather than narrow, intimate and quiet environments meant to entertain a small handful of guests.
A lot of us struggle with separating out the motivation from the change. In isolation the changes to the RoA, Fantasmic and Railroad are a potential benefit. If the change was simply driven by a desire to tighten, plus and improve the experience while updating Fantasmic and finally introducing proper backstage storage for the show - I think a lot less people would have the same concerns. But the reason these perhaps good things is happening is ultimately the companies desire to get a Harry Potter-ish over the top immersive environment into Walt's park/resort. Into a park that was built with a completely different framework then what theme parks are currently doing worldwide. Therefore the changes, while potentially good, are motivated by the wrong things and it is overall an affront to a lot of people.
On the opposite side, I'm easily guilty. Just because I'm not offended by the motivation I need to separate out what I'm looking forward to versus the consequences. Loss of formerly quiet spaces, further commercialization and expansion of a park pushed to its limits. Operational disaster looms. For some people change such as the loss of the goats really is a major blow.
Whether you are for or against the motivation, the change is not so black and white. The change is both a very good thing and a very bad thing. As all change has the potential to be. Neither will this be a cancerous change to Walt's park or the greatest thing to ever happen with absolutely zero flaws. It's a spectrum that will depend primarily on how they execute the final product. How carefully the people (WDI) institute the changes - even if the motivation behind it is all wrong.