Read the whole article. It's quite good.
It's not "youth" that's the problem. It's banality. "The best minds of my generation are thinking about how to make people click ads. That sucks." - Jeff Hammerbacher, Facebook. Most of the "app" companies are not "tech" companies. They're fad publishers. The technology for doing routine web apps and phone apps is pretty much standardized now.
The engineering that goes into phone hardware is just awe-inspiring. Electronic design today is brutal. You barely get to use any power, the budget for each function is tiny, the size has to be very small, you have to operate multiple radios without interference right next to each other, and there's a new product to get out every six months. Most of that engineering is not done in the US. That's a big concern. The US probably doesn't have the technology to build a cell phone any more.
It's not as bad as the first dot-com boom. This time, there's usually revenue. Income, even. Even Twitter claims to be profitable (although they're not, really. Look at the Generally Accepted Accounting Principles results, not the ones excluding "one-time expenses".)