I'd have to say that they would be interested because no business survives very long stagnant. If the census didn't change when they closed the backlot tour, that would be because no one, since the 80's has ever gone there to see that. They saw it because they were there and it was there. When the change over came, don't remember what year that was, it was just a little something to do. More importantly, the number of people that show up isn't anywhere near as important as how many stay there all day.
They have a reason to do something and fixing Toy Story's wait problem will not do it alone. It would seem logical that before you add something that will increase the overall attendance you need to have the old "favorites" ready to handle the additional demand. Except for three attractions (Toy Story, Lil Mermaid and the Muppets) there is very little for kids to do. The question is not why do the want to put in flat rides, the question is when are they going to do it. It would seem to me that any of the "shape pencil boys" would be sadly lacking in the numbers game if they couldn't see the potential lost revenue from not acting on the need.
You have hit on exactly the problem. It boils down to I have no use for that attraction, so it isn't needed or wanted. Besides having the expectation that man lives on dark rides alone, it just doesn't make sense that something else might be of huge value to the overall park.
One of the things that has always stuck with me when people para-phrase Walt's statement about sitting there eating peanuts while his daughters rode the Merry Go Round, that in spite of that what happened with his park when he opened it up? You cannot justify the thought that everything must be for everyone to ride without running into the conflict that his park had a Carrousel, a spinning flying elephant, nauseating spinning tea cups and motorized mini cars that travel at 3 miles per hour. Even though those, just like when he went to the park with his girls, can be ridden by adults, (brings the question, why didn't he ride it with them, but that's another topic) but, they wouldn't travel miles and miles just to ride them. The kids were the drive and the basic premise of even cartoon features were for kids. But they were made palatable for adults to participate in, but, not designed to quench their desires of things to do.