When I was a kid, I thought growing up was about taking on responsibilities and getting work done. So wrong! It doesn't matter if you're the President or you're a drunk, what makes you an adult is how you entertain yourself. If you do anything with your leisure time more fun than reading War and Peace or putting together ships in a bottle or something, you're still a "kid".
I would generally agree with you but would take issue with the word entertain. I think it's more how you spend your time, which is a finite resource.
The focus on entertainment in this culture (speaking primarily for my US experience but possibly throughout the industrialized world) is mostly marketing of passive entertainment to passive consumers for profit, like any other consumer item. The manufacturers of passive media may want your feedback, but that's so they can better sell you the next one down the line. (Joss Whedon may be much loved, and I'm sure he appreciates it personally, but if his products weren't likely to make a profit most of us wouldn't even know his name.)
I'm not sure that playing video games or watching porn result in a whole lot more than greater skill in playing video games and watching porn (with, I suppose, a substantial improvement in one's eye-hand-dick coordination). It's not that building a ship in a bottle (or any other creative activity, like writing an app or developing an Arduino project or nearly any hobby) is absolutely a superior use of any person's leisure time, or indeed makes that person superior to Zimbardo et al's hypothetical tribe of hairy-palmed joystick obsessives, but I know which activities are more likely not to bore me (or hurt someplace) after an hour or so.