How long will we continue in the same pit?

Ian Flether has a fairly devastating critique of the American Left and our utter fecklessness on economic issues. Full article here but the part I wanted to highlight is below in yellow.
This points to the second problem with the contemporary American left: it has exchanged equality as its primary goal for diversity. Now one can argue this either way, and I don't do culture-war issues, but the hard fact is that one can't prefer diversity to equality and expect equality to be the outcome. They are simply not the same thing. One can claim to be in favor of both, but strategic choices have to be made, and either one or the other must come out on top.
The real problem with diversity, from a leftist point of view, is not that it's a bad thing per se. The real problem is that diversity intrinsically tends to reduce human solidarity. Solidarity is the emotion people feel towards others that makes them care about the fate of people who would otherwise be strangers. It is thus an essential basis of any political tendency that would impose policies designed to reduce economic inequality. (It's no accident this is a word unions talk about all the time.)
Without solidarity, people don't hate each other. They just don't care. Not really, whatever they may say. Solidarity comes from having something in common with other people, and the less people have in common with each other, the more American society devolves to a model of pure individual self-interest. Which may be a leftist model in cultural or social questions, but it's a rightist model in economics.
I live in San Francisco, where there are an extraordinary number of people about who consider themselves liberal on economic issues. And so they are, when they write checks to liberal causes or participate in local political clubs and other organizations. But the other 29 days of the month or 5 days of the week, they go back to work downtown for the same corporate economy they claim to oppose on their days off. And they work hard to become rich, i.e. to acquire a nice juicy piece of inequality for themselves.
One can't blame a person for having a day job or for working for a living, but one also can't help wondering why they expect a certain economic outcome when they spend five days pushing one direction and only one pushing the other.
How long will the American Left continue to engage in identity politics at the cost of being effective? It seems at least a few more years.