I was under the impression that they could selectively remove the filibuster and not unilaterally do it and pass DC statehood via a simple majority like the GOP did to ream through their supreme court noms.
Guess we're fucked then.
You could, but since you have only a 50-seat majority, you need every member on board. Since Manchin (and Sinema too to a lesser extent) seem to be true believers in it's-not-good-policy-if-you-can't-convince-Republicans-to-vote-for-it centrism, yeah, you're fucked.
You really, really needed to pick up one or two more Senate seats than you did to pull this stuff off. 50 got you stimulus now, and it'll probably get you some decent welfare program reforms and environmental spending in the second reconciliation bill, but falling short of 52 to get around Manchin/Sinema really killed minimum wage, voting rights, DC statehood, immigration reform, etc.
If Manchin is the problem then Biden should be raising hell and forcing Manchin to change. They should make it clear that he's opposing it and force him to get in line or lose.
You might argue 'that's just giving West Virginia to the Republicans!!' but if Biden can't pass basic policies like this, then we're losing 2022 and 2024 to the Republicans full stop. At least if Manchin forced to get in line then we could get some policies passed before Republicans come in to tear things down again.
Problem is then you create a situation where Manchin's best path is to change parties, and as a Republican vote against the stimulus altogether and put McConnell back in charge of approving appointments and all that. You already have judges who have resigned so Biden can replace them. You alienate Manchin and you hand McConnell back the power to hold all those seats open for four years again. And there's still a lot of good that can happen in reconciliation bills now that all depends on Manchin.