alt Hacker Newstrump would love a government shutdown, as he has proven. I really doubt shutting down the govt would change any situation when trump is legislating by executive order, and mostly a shutdown would hurt Americans. You're trying to simplify something that isn't simple at all, and blame the Democrats for not doing what an armchair expert wants.
It's not just about what Trump wants. Most Republicans in Congress would like to get reelected.
In the comment above you suggested there's nothing congressional Democrats can do. That is incorrect. Any time the Republicans don't have unanimity, and any time they need sixty votes in the Senate, the Democrats have leverage. They need the guts, and/or the understanding of basic game theory, to use it.
Calling me an "armchair expert" and waving your hands about how things are complicated is not a counterargument.