As long as he's going to keep voting for Biden's nominees for the rest of the year I guess it doesn't matter much.
Manchin already stated earlier this spring that he won't confirm any more Biden judges unless they get Republican votes. The possibility of any senate Republicans voting for further Biden judicial nominees probably went to zero yesterday. Every confirmation from here on out could be a 50/50 affair with Harris tiebreaking.
Assuming Sinema doesn't devote her final months with some more grandstanding. I can't tell you how glad I am that we will get rid of them in congress soon.
The alternative to the Dem base putting up with senators like Manchin and Sinema is likely a quasi-permanent Republican supermajority.
Imagine actually believing this 
I think that the realignments since then have rendered this question completely irrelevant.
This is simply not true
I don't know why that's apparently so hard to understand.
The Democratic Party is a large tent. It’s simply that corporatist de facto Republicans like Manchin and Sinema aren’t welcome in that tent.
Leaving aside that, I'm not denying that voter blocs have moved over time and shifted. But the basics of how demographics act in concert or in opposition with/to each other within the political system and have expectations from it remains as it has. Likewise, corralling the votes remains as it has. Maintaining a majority coalition with trifecta control requires taking such coalition management in control as well.
If people like you managed to shut out the likes of Manchin and Sinema of course we'd have a harder time taking a majority and would have an even harder time winning large majorities.That in turn would hurt our ability to wield power altogether.
"It's good to have zero senators from deep red states" is quite a take, one that if our party's leaders shared that, we'd be a party of losers. That we held at least one senate seat in a state as deep red as West Virginia continuously for over a century was good, not bad.
I want to win. I want to have trifectas. I want to win majorities on all levels. Whatever is good practice to that end, I'll happily accept. Manchin still caucuses with Democrats. His state has shifted massively anti-Dem over the past 20 years. I'm happy he still caucuses with Democrats, who are we to claim we know how the winds are blowing better than he does?
