You have a really bleak and limited view of the far future. Species that have the means to cross interstellar space probably have found ways to alter themselves and removed their need to grow exponentially as they realized it is unsustainable, and are now perfectly content to chill on their homeplanet.

You're thinking of cancer cells with spaceships, not highly advanced beings who have mastered matter and physical reality. I recommend reading Dispora by Greg Egan, it could potentially expand your mind on what the future may actually look like.