Why I've concluded that SETI is a waste of time

After years of initial enthusiasm followed by gradually declining interest in their endeavors, I have reached the conclusion that classic SETI efforts (the search for extraterrestrial intelligence by means of searching for radio signals) is almost certainly a waste of time. Why? Because, at least limiting the answer to "close enough to here that there is any realistic prospect of even one-way communication," I have to reluctantly agree with the British evolutionary biologist Simon Conway Morris: the reason we don't see any evidence of Extraterrestrials is pretty simple. There aren't any. 

Conway Morris is a theist, but he is a scientist first. And he points out, correctly, that people have been looking for a long time not only for signals, but for telltale signs of the existence of advanced technology that should be detectable. (Not least in the fossil record, which would reveal any long past visitations of our planet, which has, after all, had advanced life on its surface for more than half a billion years). In the case of hypothetical very advanced civilizations (such as were famously discussed by the Russian theorist Kardashev some years ago), such telltales should be detectable even over moderate intergalactic distances. But nothing of the sort has been unequivocally identified, despite many years and considerable devoted effort at observation. 

The simplest (Occam's Razor) explanation is that advanced civilizations are just not common. Maybe so uncommon that in the entire observable universe (which is constrained by observable time as well as space), there simply aren't any to be observed. Even if we, as a sapient living species, are not unique, this thinking goes, we are certainly very, very rare, and we are not likely to encounter evidence of counterparts at any time in the near future, even at considerable remove.

All of which leads to the very reasonable inference that we humans, as a cosmically rare instance of the phenomenon usually referred to as sapience, have an enormous responsibility to steward the life on our planet so as to preserve our own existence, so that in the future we and the life of our planet can flourish and even spread life and civilization through space, no matter what the technological constraints. Already we know that this may be difficult, but it is not, almost certainly, impossible. But it will be impossible if we are extinct.