I'd really hesitate to say that factorio focuses on tower defense/military. There is defense, but unless you are ramping up the difficulty the bugs aren't really that much of a problem - more of a low level pressure unless you expand deep into their areas - and, you have the option to turn them off completely when starting a new game, and you wouldn't be losing a major part of the appeal (like minecraft with creepers off).
I have played factorio a lot, and at this point I'm looking for a different game, or something where the design does not include bugs in the pointless way factorio does. It's an otherwise fantastic game. Maybe it's not even wrong to have adversaries, but the way it's done in factorio is so simplified (infinite bugs from outer space) it seems like satire.
