You're missing the symmetry. The two party system is a false dichotomy. The enemy is not the other party, it's the system that causes there to be only two alternatives that are both captured by mostly the same interests. Each party convinces half the population that the other is trying to destroy them so that their votes cancel out.

And then Marx calls this a criticism of "capitalism" even though it's fundamentally a generic criticism of what happens when you centralize political power and then allow special interests to divide people into camps.