Cats these days seem more bratty and dependent than I remember growing up. And more housebound and supervised by their caretakers — perhaps the cause of the greater brattiness and dependency, a la the children of helicopter parents? Just as there has been a huge change in parenting styles over the past 25 years, so has there been with pet-caring styles, and in the same direction.
I'm inclined to rule out genetic change, not on principle, only because the change has been so sudden.
Fortunately, cats are less obedient than children toward over-protective owners, so they still get out a good bit. But it still feels like they have a weaker public presence than they did in the '80s. One of our cats used to flop down into a deep sleep right on the sidewalk out front. Once he even got accidentally picked up by animal control because they thought he'd been hit by a car and was laying dead on the curb. Another cat used to climb trees and walk over our first-story roof.
Come to think of it, it's been awhile since I recall seeing the "cat stuck up in a tree" in real life or pop culture. Last I remember was having to climb up a tree and dislodge our cat who liked to run up there, at least until the birds began dive-bombing him. That was the mid-to-late 1990s.
I'm not sure how to investigate this idea quantitatively, but it would be worth looking into by animal psychologists. There may be surveys of pet-owners over time about whether their cat is an indoor or outdoor cat.