That said, even if we put matters of the definition of 'life' aside, it is still perfectly reasonable to concentrate our search for extraterrestrial life-and-interesting-lifelike-stuff (we can call it lails for short) on planets like our own. This is because right now, the Earth is the only example we have of a place where lails has definitely arisen. We know it can happen here and in this way. We don't know whether it can happen in other kinds of places or in other ways. In other words, we know that we have a chance of finding some if we look for that kind in those places, whereas looking for other kinds or in other places MIGHT just be a wild goose chase (or a wild crystal microbe chase, as the case may be). We also know how our kind of lails looks different from a barren environment, whereas we don't know what signatures to look for marking other kinds of lails. So until we have some more data points and can extrapolate outwards more reliably, it makes sense to look in places similar to the Earth, and use approaches to detect lails of our own kind. In simple terms, to start with what we know best.
That said, statistics isn't our only tool. We actually know some fairly objective facts about chemistry and physics, and therefore can to some extent reason out what other kinds of lails might exist, where it might exist, and how we might detect it. In particular, we must remember the Anthropic Principle, which in this case implies that the kind of lails we observe on Earth is constrained by needing to be a kind that can give rise to intelligence, whereas the most common kinds of lails and environments where it exists may violate that constraint. For instance, there is reason to believe that lails may ultimately be more common in gas giant moons than on rocky planets. Those environments tend to be more stable and depend less on fine-tuned coincidences to support lails.