psyche
I wrote a long dissertation as a reply, only to realize after listening to it that most of what I wrote was simply agreeing with what you posted. Here's the short version.
First off, I absolutely agree that programs like the SETI project should continue. I'm of the camp that subscribes to the possibility of not only life, but other civilizations exist in the galaxy, despite the fact that it's only speculation at this point.
One problem I have with SETI, however, is that their search is extremely limited due to the fact that they are listening specifically for radio signals (I may be mistaken, so please correct me if I'm wrong). I would consider that as a good starting point, but there are other much more efficient means of communication, especially for interplanetary and long-range space craft chatting. A laser communication system or one which uses microwaves would be two examples that an alien civilization might employ.
But there's the problem of signal degradation across such long distances that needs to be considered. Even if an alien civilization were to point a laser directly at Earth for the purpose of sending a message, the signal would be weakened considerably by the time it reached us. The signal may drop so close to noise level that even it were detected there would be no way to decipher any information from it.
Also, assuming that panspermia was the "spark" of life on a number of other planets, I see no problem with the possibility of convergent evolution taking place, at least in a biological sense.
What I do have a little trouble with is applying the concept of anthropomorphism to a completely alien intelligent species. Assuming that life on Earth and life on our distant neighbors' planet was the result of panspermia (and also assuming that our shared biochemistry is carbon based), there is still a vast number of environmental variables that would shape the development of that alien species intelligence. There are a number of theories that try to explain how human intelligence evolved, from the need for social relationships to avoiding mating with a diseased person.
Link. But ironically, those traits can also be applied to forms of life on Earth that many consider to be operating under instinct alone.
Please bear with me while I speculate a bit. What if an alien species that resembles insects similar to those on Earth developed to the stage where they can construct and utilize advanced communication technology?
Take honeybees for example. Their hives are complex and highly organized social structures. Foragers gather nectar for the colony, workers build the comb and tend to the queen, drones mate with the queen, etc, etc. Now lets say that, for whatever reason, they evolved to the point where they needed to develop advanced technology. These high tech bees then come up with a way to communicate with each other on a planetary scale, using radio signals or other forms of technology. And yet, they would still adhere to their hive societal structure; their "lot in life" to use a quaint phrase. So the chances of deciphering whatever they're communicating to each other would be practically zero.
Yes, their colony would resemble many instances of human society; towns and cities where people work together as a whole for specific ends being the main one. But they would lack the individuality that we humans strive for (while it's true that we all sometimes feel like we're nothing more than drones and workers, we at least have BBQs and the occasional beer to look forward to).
My point is simply that even if and/or when we were to detect an actual, traceable, and perhaps continuous signal from an alien civilization, it's not very likely that they would be anthropomorphic, at least not in the strictest sense.