I disagree that children of Millenials are a waning downtrend, I actually think they are more indoctrinated into Disney. You reap what you sew. Gen Z is the one with really poor touchpoint to Disney. They are the byproduct of the 2000's output with some Cars thrown in for good measure. Plus are an echo of their by and large Gen X parents who weren't raised on home video and the animated Renaissance films.
You bring up a good point about parents passing on their love of Disney to their children
The parents of Millennials were Boomers. Those who would see Walt on TV every week, knew of the Mousketeers, Davy Crockett and more. Saw theatrical re-releases of Snow White, Pinocchio, Peter Pan.
They knew the brand at a time when it peaked, and were raising kids during another peak, when the Disney of their youth was being broadcast on TV (Vault Disney) and having it's first and second round of home video releases, along side blockbuster new offerings in the parks and theaters.
That generation was primed to love Disney, and Disney benefited from the lack of serious competition in the early 90s.
Gen Alpha are the ones being raised on Frozen, Moana, Coco, Inside Out and Encanto with the sudden home access via D+ (that has a lot of echos of the VHS wave). It's too early to make calls on Gen Alpha. But my anecdotal experience is they don't have a lack of connection to Frozen and Moana.
While Gen Alpha will form strong attachments to specific Disney experiences, I don't think Disney's sphere of influence is as large as it was in the 90s, despite the company's growth. They have to compete with so many other things for kids attention, including non traditional media that didn't exist 30 years ago. If parent's today are priced out of Disney trips (or decide to go somewhere else) than that won't lead to the same generational right of passage. American animation has grown exponentially, and non US-content (Japanese in particular) is far more accessible than it was a generation ago.
Disney pushing other brands like Marvel and Star Wars IMO dilutes their ability to raise awareness on Disney proper and I don't think the remakes are leading kids today back to the originals like some hope. Maybe that's part of the reason Wish flopped. All the literal and figurative references went over their heads and didn't have any cultural meaning.