By the numbers, WDW attendance from 1991 to 2019 (i.e. the year before COVID) is up 110%.
This is somewhat misleading.
First, since 1991, Disney has added a 4th theme park.
Second, the growth in attendance is mostly in offseason. Disney has gotten better at attracting Guests in (for example) January and September to November.
Still, attendance is up pretty much year round at the other three theme parks.
However, I'm not 100% sure if attendance is up every month. The months I most wonder about are July and August. In the 1980s and 1990s, families commonly vacationed in these months. Now, I believe family vacations are more evenly spread out throughout the year.