The ant comparison isn't meant to show that late-modern capitalist workers are ant-like in every respect. That's a strawman. The point is that even individualists (who thus lack the ant's socialist, colony-minded instinct, as it were) can be workaholics who define themselves by what they do for a living. This (obviously limited) ant-like mentality is apparent from the neoliberal solution to the approaching automation of labour: the solution isn't to prepare for an economy in which we won't have to define ourselves by our hard work; no, the solution is to trust that another round of BS jobs will arise for everyone, as these jobs always do.

You don't think neoclassical economists said that capitalist competition has ideal outcomes, ceteris paribus? The ideal outcome would be an equilibrium between supply and demand, or the discovery of the best price to clear the market and keep the economy growing. So capitalist markets wouldn't collapse or end in neofeudal indebtedness for the masses, or in the plutocratic capture of democratic institutions, and wouldn't have to be propped up by government bailouts. No, the ideal scenario is that capitalism is self-governing, like a perpetual motion machine that economists could study scientifically.

Calling the tragedy of the commons a market externality is just like saying "I don't want to deal with this whopping refutation of my pet theory's predictions." If only non-economists could get away with that gambit, we could preserve our self-reinforcing delusions against all apparent contrary evidence, by arbitrarily limiting the scope of our theories to the evidence that supports them.

Sure, the government can step in to help out the market when it fails, and to account for the downside of individualism which the classic liberals underestimated. Then again, before Trumpian populism confused the narrative, you heard neoliberals calling for more and more "deregulation" and privatization of industries. So which is it?