Space

Yes. But, much like us, the true "great filter" will turn out to be greed in one way or another.

I don't think we, as a species, are ever leaving the solar system. And I don't believe any other intelligent species would either. Exploration is high and noble, but the people who pay for it always expect a return on their investment. Finding the new world was about power, wealth and resources for those footing the bill. The exploration of the Arctic was a search for faster access to markets on the opposite side of the world.

There's no profit in doing something "just because it's there".

My belief is that we'll get into the solar system. We'll harvest its resources. And that's where we'll stop. When we think about the size of the solar system, the resources available to us will effectively be infinite. One species would never use them all up before the sun expands and goes nova. It's impossible.

So what is the return on investment to go to another star system? What's the return on investment to making all that effort?

I think we're in a universe that is filled with single-system species that just stay in their neighbourhood.