This feels like a dramatization of a tower defense game.

I don't know, I'm left feeling a bit odd about this. A few editing misses, and as we get pretty often in these things, the rhymes are a bit of a stretch, to where they'd sound okay spoken aloud but in written form are more obviously not quite there. But you start out talking about a ballista, which evokes rather old combat from centuries ago. Then you talk about exploding trip wires, which are unlikely to be used alongside a ballista, unless, again, this is from a particular game. So that made me think you were going to show the progression of military technology. Okay, net up is shredders. Don't really know what they are, but I could certainly see that being something more advanced than trip mines, so it still fits the pattern. But then "overrun" doesn't keep it going, and we're back to a ballista at the end, so I don't think that was the author's intent. I also don't know whether I'm supposed to read any significance into the repeated lines being shuffled into a different position in the next to last stanza.

This sets a nice mood of hopelssness and fatigue, but I'm not clear on how the details work.

The mood of this is "fun". From the moment we "fall out of bed" we are swept away by extravagant activity and rally cries. The imagery is neither metaphorical nor allegorical, but is rather a sort of parody of fantasy.

There is a structure here and some very loose rhymes. I sometimes wonder what the relationship is between these things and actual poetry, which, after all, doesn't really have rules. Lots of great poetry uses slant rhyme, or doesn't rhyme at all. Prose can be "poetic".

When the discipline is loose, there is a certain quality of association--"one damned thing after another". With more care with form things begin to cohere in a different way. The mind can more easily grasp the poem as an object, and pore over it. Even those "loose" poems often enough evoke convention, in some sense. But you've got to practice with it first.