[Question] Thought experiment—Does it still make sense to be an altruist if the world is coming to an end.

I came across an essay The End Is Coming by Agnes Callard a philosophy professor.

In this article, she suggests that

We may not have arrived at the end, but we have certainly arrived at the thought of it. Medical, environmental, political, economic and military problems seem to have joined forces to remind us that the story of humanity is, at some point, going to draw to a close.

and

the simple knowledge that “we are the last humans” should lead to complete ethical and political collapse.

Therefore

The Last Generation. Scientists and politicians must work to delay their arrival as long as possible; humanists, by contrast, must help prepare us for them.

So my question is, if we know for sure that we are the last generation (or 2nd last), and there is absolutely nothing we can do to change it, does it still make sense to be an altruist? Or is the last generation doomed not only biologically, but also in their ethics?