Navi River should have a wheelchair vehicle but it doesn't. It is a very difficult lift down into the boat and out again for a very short ride that has no relevant story. Pretty animatronics and scenery but it's not worth it. Neither for the wait nor the difficulty of getting on and off.
Flight of passage is not accessible to anyone who cannot ride astride. If you cannot separate your legs enough to get on a horse or a motorcycle, there is absolutely no other way to experience this attraction. No stationary seats to watch the movie. No way to park a wheelchair to seat. No way to sit side saddle or anything else.
Every other new attraction Disney built since Pandora has been accessible. They actually took the time to give alternate ways of people experiencing the attractions. And the only lifts I have to deal with are for thrill rides like Guardians of the Galaxy and Slinky Dog.
I’ve been told the reason that Navi River is not accessible is the size of the boats - they are too small to include a ramp similar to Small World and can’t have a ride vehicle with an integrated ramp similar to Buzz Lightyear, Imagination or Finding Nemo because of the real water.
And, the reason I’ve heard the boats couldn’t be bigger was budget cuts to the attraction. The size of the attraction was apparently cut meaning they also had to cut the size of the boats to fit turns and spacing. Another casualty of bean counters versus show.
My family found Flight of Passage to be an easy transfer for our daughter, but that’s only part of it.
My DH lifted her leg and arm from one side and I lifted from the other. They also have a clever transfer wheelchair. BUT, as you pointed out, transfer is only part of it - guests need to be able to separate their legs enough to sit astride it
and stay in that position for about 4 minutes to ride. My DD did fine and enjoyed it for the first 30 seconds or so, then wanted off.
I can see why they couldn’t safely have a side saddle position, given the motions during the ride. But, they could have made an alternate experience in a stable theater. For example, the movies in China and Canada (and even France) give the illusion of moving while you stay firmly on the ground.
Many of the newest attractions - Slinky Dog, Mickey & Minnie’s Runaway Railroad, Guardians of the Galaxy and the upcoming TRON ride all have alternate ways to board. But, because of their motion, they shut out a lot of guests. They are not safe for my DD and since Guardians made me very sick, I’m not likely to try TRON.
The Runaway Railroad doesn’t have a wheelchair car like Remy’s Ratatouille Adventure. It does have a nice, dedicated accessible loading area, but the small opening on the side of the vehicle makes it a challenge to get in and out.
My DD rode it once and enjoyed part of the ride, but because it has a slippery bench seat and a grab bar instead of seat belts, she felt very insecure and needed support from DH and I to keep from sliding around. Remy is a pretty similar ride, but Remy has a very nice wheelchair accessible ride car.
She’s not a fragile person and loves thrill rides - if she feels safe. She loves Tower of Terror, Mission Space Green, Test Track and especially loves Rise of the Resistance. I think she would also like Smuggler’s Run, but because the individual seats have no side support, we don’t think it would be safe for her - that’s another situation where a small change in the ride seats could have made it more accessible to more people.