On this, we completely agree. I think the "lost decade" at WDW from 2007 - 2017 (basically post-Everest up to Pandora opening) will, in time, be seen as the worst period for the resort in terms of park investments*. Did some things get built? Sure (Toy Story Mania, New Fantasyland), but not nearly enough to service four theme parks. Spending a billion (at least) on tech and wristbands was a gigantic mistake that forced the parks to tread water.
I do think Staggs was more a fall guy than not, though.
* For the overall quality of the experience, obviously Chapek's time was worse. There were lots of projects happening under his tenure, though.