Democrats have a slim majority in the senate, which is not enough to get whatever they want done without compromising, especially considering that two senators are not as left wing as the rest of the party.
As far as war and military spending goes, I agree that the party could do better.
That’s not really how it works. It would only make them look stupid if they did that, and increase the risk of being voted out in the next election. Because of the filibuster, legislation generally needs 60 votes in the Senate before it goes to the president. Democrats have 51 seats, with two frequent defectors. Imagine if Biden’s record going into 2024 is that he vetoed every single piece of legislation.