You can point to those civilizations because their collapse was not the end, life continued on. We haven’t been hit by a gamma ray burst or any other complex life ending disaster since we are here to discuss the scenario. But that’s no guarantee that we won’t be.
The odds of anything happening to render Earth totally uninhabitable are very small… in our lifetimes. But as long as we keep existing, the time frame will keep growing, the opportunities for disaster will keep accumulating and the odds will keep multiplying. The basic math looks very different when you multiply by infinity. Even the sun won’t last forever.
Obviously, this is no reason to neglect Earth and rush to other planets. But it is reason enough to reject the idea that we should never spread to other worlds because Earth will always be enough.
I look forward to someone making an appropriate oompa loompa song for his exit.