It’s not a moderate problem it is a math problem. The median Senate seat is R+7 partisan lean. It takes three cycles to create a new Senate. The 50 Democratic Senators represent over 60% of the American population.They have complete control only in name alone. Faux Democrats like Manchin will ensure that nothing substantial will actually be passed. The Democratic party will remain screwed until it deals with its moderate problem.
The other issue is progressives are fair weather voters. Conservatives vote consistently in every election. They recognize that it takes decades to reshape the US political landscape.
We went through this in New Jersey with our super progressive governor Phil Murphy. He campaigned on $15 minimum wage, legal weed, etc. and with a heavily Democratic legislature (not 50-50) it still took over three years of his first term to get these things passed.
Six weeks into Biden with a split Senate and progressives are already ready to cancel him.