WDW needs to spread their rides among 4 parks compared to Anaheim's two.
Both Orlando and Anaheim have just about the same amount of rides, but with WDW, they're spread out more.
Anaheim, short of their DisneyForward expansion (that may never come about), can only add new rides by cramming them in tightly in the space they have.
I do believe the company is banking on that logic prevailing. But Disneyland CA expects you to spend 2-3 days at the park, compared to the 5+ days WDW pushes for. (I had to look it up: WDW sells up to 10-day multi day passes. Disneyland sells up to 5-days)
In encouraging at least double the amount of days to WDW vacationers, they’re over promising and under delivering. That kind of that “the guest is too naive to notice” cheapens the brand.