A stable step-ladder is an easy alternative to "building a jungle gym", but either way, you can wrap some rope or even rags around parts of it for better grip (traction). Do make sure it resists tipping though- that's admittedly harder to do with a big & very strong snake.
I personally use a lot of natural branches for my snakes: I angle them crosswise in their tanks so they cross over & interlock in the middle, which keeps them very stable. (You can make sure they don't slip by using a twist wire- no sharp edges please!- or a zip-tie for more strength & permanence.) My snakes love to climb on them & often rest in/on their branches.
As already mentioned though, a snake that's never had these things may take a while before they'll use them- but don't let that stop you. The sooner you provide them, the sooner your snake will explore them, & that exploration may improve appetite as well.
You CAN totally fix this, y'know.