Personally, I agree that cost per ride is a bad way to calculate WDW value. I've done that mental math at
Disneyland before, but I'm absolutely confident that you can check off more rides per day at DL than is possible at WDW, given the density of each park, the number of attractions, and the corresponding lower average attendance rate per park.
I'm honestly not sure that the experience has suffered over the years. Tracking opinions over a longer period of time, one would think that things were constantly getting worse over decades or that staff has been cut and cut and cut, perks taken away, and favorite experiences shuttered. I think that the quality ebbs and flows, but is still generally world class and ever expanding.