[mman]

It's also possible (more likely?) that life on any nearby planet discovered would just be a failed attempt of our own. If this is the case, then its discovery would actually be good news, it would mean we can continue in the face of catastrophe. I don't think the author touches on that.

We already know of at least one catastrophe we are rebuilding from, there's also no reason to think we weren't already rebuilding from earlier (possibly much larger) catastrophes.

Following this, there's nothing to say that we haven't already had some major effect on our surroundings (intentional or not) in some previous, possibly more complex or larger-scale growth. Our influence on our surroundings could be huge. Lack of life or anything that seems anomalous in our immediate vicinity could be our own doing. A seeming lack of evidence for this might be explained by scale, or the nature of the catastrophe, or (if it was intentional) by design.