The point isn't that it can't be done, it's that voters are strongly incentivized against trying, so they only do so when the political system is completely bro

The point isn't that it can't be done, it's that voters are strongly incentivized against trying, so they only do so when the political system is completely broken and they feel like they have nothing left to lose, or they feel like there's such massive support for their third party candidate that the party shift has already occurred. It's a chicken-and-egg problem. Depending on that to fix problems with the two dominant parties is like seeing an infection and doing nothing to treat it until gangrene sets in and you have to cut off their leg (and give them a robotic prosthetic that you hope will be better than their real leg). It can and does happen, there's even a term for it, iirc: electoral realignment. But it hasn't happened recently, despite a clear sense by everyone that our political system is broken and stupid. Ross Perot tried to incite one in '92 and look what happened.