Yeah, but really the evidence points more to sentience being an advantage, as demonstrated by our outpacing of every other species on the planet save the oldest and most simple (viruses and bacteria and so forth). I mean, yes, we only have ourselves to examine, but consider that intelligence wouldn't have occurred if evolution hadn't selected for it. The odds are really good that life generally exists in the same way that we do because that assumes that we're the norm, and not some special case! Assuming that sentience is a dead end is actually much more of a conceit than assuming that sentience arises in the normal course of events, because it's still saying that getting to this "dead end" point evolutionarily means some special set of circumstances has happened to naturally select us here that wouldn't have happened anywhere else in the universe...