I think your take ignores a bunch of important factors
Like what?
I'm honestly curious.
because I don't see how any democrats no matter how moderate could ever float the idea of compromise again. Republicans have proved it will never happen.
-The Dems need a super-majority to pass a comprehensive single payer program. Any realistic shot of that happening died with poor tunrout in 2014, and missing the chance to put 3 more liberal in the Senate in 2016.
So if liberal vote constantly, best case scenario is probably mid 2020s. If a Dem wins the presidency in 2020, then the right wing base will be looking for revenge come 2022 midterms. So liberals have to start voting in midterms constantly.
-Second a Dem super-majority might not be enough, because any left wing healthcare bill will have to pass the most conservative Dems. So you have a situation where 2018 might be a blessing an a curse. If the three moderate Dems keep their seats, they might play Libermann down the line, if they lose their seats (opening the chance to run more liberal candidates down the line) then you put off getting a super-majority.
Joe Manchin doesn't give a **** about what progressives, young people, or single mothers want.
-Without a supermajority they could in theory just lower the age of Medicare, or allow everyone to buy into Medicaid, but they will still need to fund it. Another possible road block because the cost of single payer will be put on front street. Now you have to raise taxes to fund the program, this will have major political backlash
-While single payer is popular in theory, if is not as popular when people learn the ins and outs. The economics of the program is not as simple as most believe, Bernie Sanders is over promising like a mother ****** when it comes to his proposal.
-Private insurers and right wingers will sue constantly and with a conservative Supreme Court, single payer might die before it lives. Just ask Obeezy about the Medicaid expansion. Throwing together a bill hastily will make this more likely.
-Also in America, private insurers play a huge part running our publicly funded insurance programs. Medicaid is mostly private insurers that administer it, Medicare too. Supplemental private health insurance plans are a big money business in America too. So will private insurers take a hit, of course, but will it be the end of them...... Nope
Unless you block them from selling to firms, and administers Medicare, Medicaid, CHIP, and all the other government funded plans through new formed government agencies (another thing you might need a supermajoirty to set up). The private insurance industry is not going anywhere.