Michael Crichton's
Sphere has a good section about the "anthropomorphic problem", about how we imagine extraterrestrial life as essentially human. Regardless of how they look, they still act human in our imagination.
Why apply concepts like "rogue", "mission", "rules", or even "individuals"? There's no guarantee such ideas mean anything to these things. For all we know, the UFOs themselves are not actual artificial spacecraft, but "biological" entities. Or autonomous drones.
Or they're not even extraterrestrial, but visitors from the future. Or some sort of interdimensional phenomenon. Or they're some sort of mythological being out of human religion- perhaps Abrahamic entities like the Angels of Mons. Or that they're the manifestation of mankind's collective unconsciousness, a sort of high-level tulpa. Or they're just some kind of weird unknown cosmic particle, a high-altitude form of quantum ball lightning.
Those possibilities are tongue-in-cheek, but my point is that if you're going to start assuming that UFOs are just spacecraft from an unknown alien race... then you start making assumptions upon assumptions and the whole thing just devolves into science fiction tropes. And honestly, those tropes are no more probable than the crazy Fortean explanations I've offered. It's fun to talk about, but why take these thought experiments seriously?