I don't see this as an age question as much as a boss/owner call out the chute.
If you generalize, you will see much more of a younger crowd who can't deal with work or even authority. It's what's in the schools, what politics are doing and then the biggest factor, your home-life.
Work ethics are first learned at home. If you were raised with a good working code, you're bound to be a good worker.... or at least eventually fit in. Without the work code, you're bound to be a loser or a quitter. I have a kid who just turned 18 and works part time wit me and he has some of the best habits I've ever seen. Everything is..... yes sir, no sir and yes, I can do that. He helps and is thinking as he goes along. He has the next tool ready without my asking. He anticipates and he asks questions if he doesn't know. Outside the shop and inside, he is one of the best workers I ever had. I have people who have worked here for years, they constantly challenge things, things that shouldn't hafta be explained..... or discussed, but I figured it out some years ago what's going on. If they discuss how to do something or debate what might be better, it sounds all good and whatnot, but all it is..... is a time waster. They get outta work while we stop to talk and inevitably, they never win, cause their appraoch was bassackwards.
Back to the age thing. Again, while I don't believe it's an age thing, altogether..... it is on the person hiring to at least keep up with things and if they've made a mistake in hiring the wrong kinda person..... get rid of them. You don't just keep someone on board to fill a spot, if all they do is suck up air and money.
So, ya set a good precedence and keep everyone working at a good pace and when one starts to falter, ya write them up. If it happens again, they're out. I have a 2 strike system, not 3. So, it's the person doing the hiring who is to blame and making the whole barrel rotten, cause that's all anybody sees.