there's a big difference between how we spend the accessible resources in the universe and how we avoid wasting them all, burning the cosmic commons in colonization and evolutionary arms races that destroy most of the potential of our accessible region.

The universe appears to be bountiful. If we don't do something like this, probably someone else will, obliterating us utterly in the process - so the question is: would you prefer the universe to fill with our descendants, or those of an alien race.

We don't have to fight and compete with each other, but we probably do need to have the capability of competing - in case it is needed - so we should practice our martial arts.

As for universal conservation, it's possible this might be needed. The race may go to those who can best hunker down and hibernate. Ultimately, we will need better cosmological knowledge to know for sure whether cosmic restraint will prove to be needed.