So here's the rub, then, the only solution to the problem of "democrats and democrats lite" (which is a problem I agree with your framing of) is to reform one of the two parties from within. Or kill it and replace it. The Whigs were replaced. The GOP is getting transformed into the MAGA party. Meanwhile, the democrats are not going to break into a Green party and a Progressive party or some such, they are actively purging moderates, JFK democrats as it were.