I hear you, but this is overlooking a crucial point (or points)
EuroDisneyland Paris (when it bore that name) was as good as WDW. It was even better because the park (
Disneyland) IS better than MK in many aspects.
The fact that WDW is older is not an advantage in the sense that its age allowed for a better development. DLP was better in the first place. And what's sad is that DLP did not use its 20+ years to develop and grow, but instead it went down a slippery slope, each year giving less and less to the guests, until the low point of 2013 when many guests think that enough is enough
On the other hand, WDW's age is a great disadvantage, because WDW is in Florida, and Florida is very hostile weather. Even if Paris has cold winters, the rides in Florida (and California for that matter) go through a lot.
And when a park grows old, it's native attractions, rides and themes grow old too and age fast, and need more maintenance.
Can you believe that a Vekoma's engineer declared that Space Mountain looked like a 50 year old coaster. Space Mountain was opened in 1995 and its track are in such a bad shape that it's in a worst condition that it's counterpart in Orlando (1974) and Anaheim (1977) (Vekoma is the Dutch RollerCoaster manufacturer who built Space Mountain)
Is age really an advantage ? I don't think so.
If you want to make an "age" comparison, DLP is now at the "teen age", you know, when they don't want to hang out with the parents, they don't want to do anything, they don't shower anymore, they don't care about anything ... that's our park, and just like our teenagers we still love it from the bottom of our hearts, but that's a time where you really need to kick them where the sun don't shine ...