I think the coaching, from the minors on up, has been preaching "slow the game down, make the other guy wait, make him give you your pitch (or swing at the pitch you want to throw), put it on your terms, not the other guys'..." They've been training the players like this for a while, now.
So, you get pitchers who try to stare down hitters or baserunners, or batters who try to wait until right before the pitcher starts to move and then steps out.
The MLB game has been mind-fuck baseball for quite a while. It's just been getting more and more codified and trained-in for the past couple of decades. And that ends up slowing down the game somewhat.
It's the extra commercials, the waits for challenge decisions, and more than anything else the much larger number of pitching changes per game, and their associated inning-break-length commercial breaks, that have been making the games significantly longer.
That said, I
really don't mind if the games run three and a half hours, when they're exciting. And I've seen a
lot of very exciting nine-inning games that lasted three and a half hours. They were usually high-scoring, with lots and lots of coaching moves. Great, fun games.
It feels like they want to give me less entertainment per game. And I don't like that.
Baseball is the one game left that is just supposed to end when it ends, nothing forcing it to try and rush and end on some mythical "on time" embraced by people who don't know when to breathe if it's not marked in their day-planners.
I firmly believe that even the millennials will welcome coming back to this game, as it exists now, in their later years -- a place where they don't have to be in such a damn-fool
hurry...