The Myth of the Myth of the Independent. They aren’t just closet Democrats or Republicans but span the political spectrum with many not tilting one way or the other.
In some states there are more Independents than Republicans or Democrats. This indicates huge and growing disaffection among voters.
The two parties have seized control of our political system and deliberately make it difficult for third parties to gain ballot status. Further, neither parties wants increased voter turnout because that might upset their cozy little duopoly. They benefit from and encourage voter apathy.
Change is possible. The Vermont Progressive Party is now a major party in that state and their senator Bernie Sanders is an Independent who calls himself socialist.