When Disney World opened in 1971, it was the only game in town...so catering mostly to families and children kept it thriving. But over the decades, the area has changed - and now there are many competing theme parks all around, varying from kid-focused to action rides for teens and adults. Disney has stayed relevant by being much more immersive, heavily themed, and catering to the grown children who grew up going to Disney parks and now come back as adults, sometimes with families and sometimes as adult friend groups.
There was a time after Pleasure Island closed when Disney World was stagnating and not providing anything for adults, so even many grown kids who used to go to Disney parks stopped. I know this because I've always gone to Disney and had many friends who did as well, and nearly all of them lost interest and didn't want to go. To them, it was just kids and kiddie rides.
Over the past 15 years, all of the adult-oriented additions to the parks, with rides, theming, resorts, restaurants, bars, festivals, and adult-only spots have helped bring back many of my friends. I talked them into trying Disney again, coming with me and doing the parks 'my way', with focus on not just rides but great food, bars, live music, and other options...now 5 of my good friends regularly come to Disney World with me, or go on their own.
And yet families and kids are still clearly the primary attendees of the parks - they're all around, having a great time just as we did when we were kids. Rides, shows, characters, and theming for children is still omnipresent throughout the parks - but now, there are ALSO rides, theming, food, drink, and entertainment for teens to adults mixed in alongside. So Disney is playing to all ages, as Walt intended...kids, kids at heart, and adults who grew up with Disney. And even those adults who bring their kids now have some places where they can be entertained while the kids are doing their kiddie rides and shows. I see plenty of parents taking a break from the kiddie stuff - a dad getting to stop off for a beer at the Tap House while the kids play in Toy Story Land or Galaxy's Edge...or enjoying a food booth at Epcot while the kids hit Remy.
When I was going to Magic Kingdom in the 70s with my grandmother, we were ages 4-10 and would go on rides while she waited outside (she didn't like most of the rides). What was her entertainment while waiting for us to go through the line and ride the ride? Nothing - she sat on a bench bored out of her mind. She did it for us...but now, that same grandma can see some art displays, listen to a band play, have an adult beverage, sample some international food while waiting and people-watching. She probably would have given her left arm to have had those options back then!