We don’t know what we don’t know. Warp drive (Alcubierre drive) may be possible. The interesting thing is that it was first thought that warp drive may require the conversion of mass equivalent to Jupiter, but now, not so much:
[NASA researcher] Sonny White revealed a new design (pictured top) for the Alcubierre drive that reduces the energy requirement from the total mass-energy of a planet the size of Jupiter, down to the mass-energy of Voyager-1 (700 kilograms).
Like always, the theoreticians show it’s possible, and then it’s “just” a matter of the engineering…and the endless streams of profanity that are part and parcel of engineers’ opinions of the theorists.
When it comes to “cooperation” being a requirement, I’m sorry, but we can’t know that. Perhaps they’ve got a species-wide obey-at-all-costs ethos like ants or bees. Perhaps they’re all individually controlled by a central intelligence. Perhaps they do have cooperation, but only within their own species. Perhaps they have some sort of religious requirement to kill all other species.
We don’t know. We can’t know. And the Dark Forest’s point is, the other species also face the same set of uncertainties concerning humanity.
So it all really depends on whether you would gamble the existence of humanity on whether your personal assumptions concerning extraterrestrial species is right…and the other species faces the same gamble.