You said, normally you get along fine, just not this time. What makes you think it's an habitual problem with the entire generation, and not just one moment of "I don't want to be disturbed right now".
Would you interrupt someone reading a book the same way? If yes, kinda rude in my opinion, because I'm not doing nothing at the moment, I am reading. I don't have time to talk to you right now because I am occupied. Ask "do you have time for a small chat?" and if the answer is no then move on. 20 minutes is certainly overstaying your welcome.
As to the other stuff you wrote, just seems like a ramble without a clear direction. You seem to imply that the societal norms you grew up with are "correct" and that they shouldn't change