If you don’t believe that the vast majority have given up, talk to a few twenty-somethings about key political issues. They, rightly, see a system that’s rigged to support the needs of the olds at their expense. Medicare is treated like a fucking sacrament, but it’s a sin for the young to take Medicaid. As employees without much experience, they are entering jobs in a world where the baseline minimum wage is a poverty wage, and nobody will hire them full time without a college degree and the debt necessary to attain that credential. Obamacare improved their lot a bit, but that (for them) extremely minor improvement came after an ugly fight that was completely out of proportion to the real benefit of that legislation. After Obamacare, the government basically shut down for 4 years, and it was pretty clear that 2014 wasn’t going to change that, so remind me why they should have voted?
This post gets to the heart of the problem with the "coming Democratic majority" argument, that is, the assumption that even if Democrats have irretrievably lost the votes of old white people, they can count on the shifting demographics of American society to start swinging elections their way.
These growing demographic groups may be inclined favor for the sorts of policies that Democrats tend to support. Even if that is the case, that inclination does not translate directly into "They're going to vote for Democrats." In fact, if the Democratic party continues along its current path of attempting to find the most tepid position possible on every single issue, it is straight-up insulting to would-be voters.