DL and DLP show you can get a lot of use out of the rivers. MK just doesn’t want to put in the effort. Eddie Sotto and Jim Shull both made mockups for ways to have a “best of both worlds” situation. I also made one myself (but I’m in bed staying up late when I shouldn’t be to talk about cartoon cars and rivers).
To me, the best case scenario is cutting the river in half, putting Cars on the back half and leaving the front. Either keep the rafts to the island or add a bridge/tunnel for people to use to get to the island. You get the walkway that connects BTM and Mansion, you get Cars, and you keep the scenic views of TSI and the riverboat. Everyone wins.
Also, imagine if they kept the island and built a nice waterside dining location where Aunt Polly’s is. The views at night looking towards the Mansion/LS would be beautiful- plus the fireworks- and you could make a ton of money through reservations!