There's no real evidence to support this because Disney overwhelming only builds IP attractions, and as such, hasn't really had any point of comparison to draw such conclusions from over the last 20 years. If anything, the enduring popularity of older, non IP staples like Big Thunder Mountain and Spaceship Earth over things like Little Mermaid suggests guests are capable of drawing their own conclusions on quality if presented with more options.
@lazyboy97o already pointed out that Everest cost far less than subsequent IP rides to build, and that Iger made up his mind long ago, without much analysis or understanding, that IP rides were simply better.
You're falling into the same trap so many Disney fans do. Thinking that because corporate Disney decides to do something, must mean that it was the most logical option to select. Or that past failures were because of the last guy in charge (Chapek, Eisner, Ron Miller) and as long as the current CEO keeps his job it must be because he's doing everything right.
That ignores the entire history of the company, one fraught with poor financial decisions and assumptions about their audience and expectations, and was impacted negatively or positively by external factors beyond its control