The universe was spinning 8 billion years before our planet even formed. We went from hunter-gatherers to visiting Pluto in just tens of thousands of years. 99% of mankind's technology has been created in just the last few hundred years.
Imagine what a civilization could achieve with even a 100,000 years head start on us. Then consider they could have BILLIONS of years head start.
I think the opinion that no civilization could last that long without destroying themselves is close minded. That's assuming a closed system. Easter Island is a good example of this. So is a planet.
But if we could travel the stars such problems as politics, famine, war would be inconsequential. Also spreading your race across worlds would increase your chance of survival not limit it. Pretty much all our issues stem from resources. Space travel, hell even mining asteroids would solve a lot of that. Imagine claiming not just a continent but entire planets.
Worrying about light speed is also naive. We don't even know how our own universe works. We didn't know how electricity worked 300 years ago. There could be means of travel we can't even conceive of yet. Spooky entanglement is totally a thing. How does it work? Could these underlying substructures to space time be exploited?
To say space travel is limited to what we can achieve with our current combustion based propulsion methods is like Ben Franklin getting zapped by a battery and assuming it could never be harnessed into a super computer.