It's kind of hard for me to quantify, in that their relationship (and it is all three of them regardless, if I remember correctly) is definitely a major part of the narrative and in a way its driving force, but it doesn't in any way feel like a dating sim?

Which people you "choose" to have scenes with just determines which of their visions of the future becomes the ending, because all three of them want a different outcome, but they stay together regardless. The mecha fights are a partially-literal metaphor for interpersonal conflict between them over humanity's future in space, which is why the tagline is "Win for your ideals or lose for love, and grasp heaven in your hands." They either push forward with what they personally want or "lose" by agreeing to a different idea.

So I suppose it depends on why you don't like romance in your VN! If you don't want to read a love story at all, that is what it is, but it's not obtrusive to the rest of the plot because it essentially is the plot. It's a romance in the same sense that Slay the Princess is a romance.