With this mindset, progressives will never enjoy success, and the rightwingiest democrats will rule the roost forevermore, offering platitudes to the left flank which will be successful because progressives have nowhere else to go.

It is the same narrative up here in Canada. Trudeau's Liberals will be in power until they mess up covering up their plutocratic desires and corruption, at which point the Conservatives will take custody and hold power until they aggravate enough people by eroding public institutions, at which point it will be passed back to the Liberals. At no point in this pattern will the government stop working mainly at the behest of the wealthiest 0.1%.