So make at least one of them a party with reasonable policies
Give them a voting base that they can do that with. You can disagree with policy all you want, but if the votes aren’t there then it’s hard for politicians to justify voting against their constituents. You’ll just get the present situation where a smattering of politicians support more left policies, but most Democrats are center-left.
Of course people care. That’s the lock-in.
Okay, but the problem is that those third parties have no chance of winning. If you deny the closest viable party your vote, they will just move rightward to try to capture votes they think they can feasibly win without alienating the middle. Stubbornly sitting in the extremes gets you little in situations where you have to compromise.