The larger point is that the government is already shut down, and has been for several months, as the Trump administration initiated an assault on this system of government. Activities deemed “essential” by the president—stalking immigrants, lobbing missiles at Iran, etc.—have gone on, but activities purported to conflict with the president’s policies, regardless of whether they have been authorized by the lawmaking body of the United States, have been stopped, interrupted only by occasional federal courts telling the president that doing so is illegal, which the Supreme Court subsequently brushes aside.
Democrats will cave because their bosses (corporations and billionaires) will tell them to.