[GingisK]

But physics applies to all physical beings. It seems impossible, physically, for ET (or us) to travel at light speed for years to visit wherever, and then go home etc. It’s just not going to happen.

You seem pretty sure that we know everything there is to know about physics. Here we are, just 200 years or so into that study.

[DoodleBob]

Quite the contrary, what we know is scratch.

At the same time, we know enough.

Absent technology that detect a speck of rock and can make a light-speed traveling machine side-step it, this is a gating factor.

[Svartalfiar]

The problem that stems from this worry (lack of problem) is that us announcing our presence is still extremely contained. Unless these super-advanced aliens live right next door to us, it's just not possible. Aliens from another galaxy simply cannot have 'seen' us yet. Outside of faster-then-light travel / communication, even other beings in our own galaxy wouldn't have seen us yet. The only, tiny, man made objects that have left the solar system are essentially still on our front porch. Our initial radio broadcasts have barely made it halfway through the neighborhood (and at this point are weaker than the universal background noise).