I definitely hear what you're saying about kids emulating what they see in the NBA. Just yesterday I was working out with my daughter (who plays college hoops) and there was a bunch of younger kids playing pickup. They ALL were doing the Harden step back from three. And made about 5% of them. I'm thinking, if I'm guarding you, and you want to do THAT, by all means, do that til your heart's content.
I also agree that a big part of it (as I think I've mentioned) is that at every level they run NBA-style offenses. College (D1 through D3), high school, even middle school, they're looking to take a ton of threes. But at those lower levels they don't shoot it well enough to justify it, and the vast vast majority of those kids will never play in the NBA, so I don't get why high school coaches are orienting their offenses around a skill set that the vast majority of their players will never have.
Anyway, I'm sure you guys are all right in terms of why things are the way they are. Maybe it's my experience coaching (where I still coach HS girls to get to the block...yes I know it's girls so maybe that makes a difference...but my teams are very successful at it) and even playing (where I roast college kids who used to be very good high school players on the block even though I'm 30 years older than them). I just think, man, wouldn't you rather get a shot from 5 feet than from 10-12? If you can get to the rim, yes obviously. And if you get a wide open three, yes, obviously. But after those two options, isn't a good post player the next best option?
I guess my view is out of date though. Heh, not the first time for that.
EDIT: PS - things do come and go in cycles. Funny you should mention running, because the Patriots won their last five games of the year (and a Super Bowl) by running for 889 yards (178 a game) while throwing for 1305. That's one passing yard for every 1.47 rushing yards. To show you how big a departure that is from their recent history, compare that ratio to their past 5 seasons (which included 4 trips to the Super Bowl).
2014: 1727 rush, 4291 pass, 1:2.48
2015: 1404 rush, 4812 pass, 1:3.43
2016: 1872 rush, 4456 pass, 1:2.38
2017: 1889 rush, 4619 pass, 1:2.45
2018: 2037 rush, 4405 pass, 1:2.16
Last 5 of 2018: 889 rush, 1305 pass, 1:1.47
It's not just "matchups" either. Yes, the Rams and Chiefs were bad against the run so that made sense. But Buffalo was #10, the Chargers were #12, and even the Jets weren't terrible at #19. So they were able to run well. Anyway, this is a major digression. Just wanted to say that I think that as things change, the good teams adjust off those changes. See how the Patriots do things. Maybe it's harder in the NBA than it is the NFL. I just think you can zag when everyone else is zigging.