You are thinking out side the "narrow" confines of reality. I don't really even understand your argument. Let's look at the facts.
1. The party in power has an enormous amount of power, not just to win votes but to set committee leadership and control the agenda.
2. Third parties align themselves with one of the two main parties because they aren't stupid and they have no leverage if they don't.
3. This state of affairs is a direct result of how our winner takes all system of government is set up.
If you can't accept reality, and you can't suggest any realistic way to change reality, then I don't really get your point. You haven't argued against this points. Nor, have you suggested any way to counteract them.
You have every right to vote for a third party, or to vote for someone in the other party then the one you support based on their noble character.... but it doesn't make any different. The party that is in control matters more than anything else.