Earlier proposals included increased funding for border security. However, the Democrats don't support a full-length border wall, and that $5.7 billion was going to be used to help get it underway (under less-than-honest pretenses).
And besides, there are many good reasons to oppose a border-length wall. It's extremely wasteful; it'll be ineffective unless there's tight human monitoring across the entire length, which won't happen; it'll likely require seizing private property, creating disputes and delays; it'll produce lasting ecological damage to species that need uninterrupted terrain.
I'd also add once more that another shutdown would only further assist the Democrats. You want Trump to stand a snowball's chance of winning in 2020? Sideline the wall. If he wins next year (and that's a big "if"), he can use that as a mandate. He made the initial proposal as a campaign promise without any clue as to how it'd be funded or how it would work. Now that it's confirmed Americans will pay for it, and that it will likely take tens of billions of dollars, Americans can decide if it's actually worth the cost (hint: it isn't).