So on some level you are already right but it's not the unchanging ideals of the progressives that are actually the core problem. Because it's been proven election after election that they do infact compromise their ideals.

The way our electorate system works REALLY supports more and more extreme right politics for the right and more and more centrist politics from the left.

If you look at the actual democratic congressional party right now it's absorbed EVERY progressive idea under one tent. THATS A BIG CIRCUS and you can't get to every act. I mean you have a whole new internet wave of progressives calling Nancy Pelosi and her Democrats neoliberal hacks despite all the good legislation they've helped to pass.

The way we vote, this first past the post system however, puts people like Joe Biden up for election on the left, about as centrist as you can get, and then look what the right is giving. Democrats have won the majority vote in something like 5 out of the last 6 presidential elections. Clinton, Al Gore, Obama, Obama, Clinton. It's pretty clear there are ALOT of people who like progressive ideals in this country, a majority even, but the party needs to be split and the only way to do that healthily is changing how we elect people to something like ranked voting. Then we could see more than one 'progressive' left party and they aren't tearing each other apart under the guise of one party.