The novel states that the Machine is not a wormhole generator, and obviously, it doesn't have to be. The Aliens already have wormhole generators. They can fashion a hole through to us easier than transmitting the means for us to go to them. All they need from us is the destination, a specific time and place through which they can enter our space. All they need from us is a 'now.'
Thus the Machine represents the last piece of the wormhole puzzle, the final and simplest link in the functionality of the wormhole network. Its only purpose is to make a small dent in spacetime to which an awaiting wormhole nozzle can attach. The Machine is only a spacetime marker.
It could have been anything, but for proper dramatic reasons Sagan chose a device that has 'weighty energy' for his novel. And because international cooperation was a major theme in his life he also made it hard to build, forcing humanity to work together, more or less. The movie Machine satisfies these goals in some ways, but not in others.
I like the rings. They have power through shear size, and I like the way they resemble an electron shell. But the other more dangerous elements of the Machine are a transparent effort to manipulate the audience. For example, the fireworks display when the Machine fully activates is just a lot of noise. Maybe it's there to distract us from the complete lack of interesting dialog or a satisfying ending.
The drop/catch mechanism, the needless conflict over the inclusion of a chair, the goofy thing where Ellie's face peals itself off her head, the pod becoming transparent in her line of site and the child-Ellie face substitution have no intellectual justification. They are a discontinuous assemblage of unrelated nonsensicals.
Why have her drop through the machine at all? It's not dramatic as much as it is a thrill ride. This movie should be smarter than that. Couldn't she be somehow suspended in the center, thus avoiding the need for a drop/catch mechanism?
The special effects for the machine/wormhole journey are very good, technically. But how good are they really without a strong foundation in logic and storytelling?
I beg of you, make sense.