100% my problem with this. We're applying a human-centric lens to this. Remember that these theories are based on a life-form that evolved completely separate from anything we have ever known. That doesn't just mean separate body structures, but an entirely novel and completely unknowable circumstance.
This is why these theories all upset me - they should all say things like "we should have seen (an alien species that is similar to us) in this amount of time.
Because fuck only knows what an alien who evolved in a system based on helium or some other gas would think. We certainly can't try to figure it out. The most creative minds in this area are those writing hard sci-fi, I would argue. And most of them only treat that subject with a hand-waving and 'we can never know those mysterious aliens' sort of thing.