There is, as yet, no hard evidence that the laws of physics vary throughout the Universe, and quite a lot of evidence to suggest that they do not. But in any case, it hardly matters what aliens billions of light years away can or can't do. What matters (if they want to visit us) is what is achievable *here*.
It's extremely unlikely that aliens have visited because you have to take at least several considerations into account. First and foremost, it's not even clear how likely the chance of such life emerging in the first place is. There is some suggestion that complex life emerging on Earth is more or less an accident, for example. If it's accidental, then the chances of complex life developing elsewhere are already small. Presumably non-zero -- what has been an accident here could clearly happen elsewhere in the right conditions -- but small nonetheless.
The second generation stars TTT mentions are also related, because that places a time limit on how long such life will have had to develop, etc. I'm not sure how significant the restriction is because I think it only knocks a couple of billion years off the available time, but it acts as another constraint all the same. Taken all together they at least squeeze the chances of life, let alone multicellular life, let alone intelligent life, let alone technologically capable life... emerging.
None of this is undermined either by what we don't know yet. I don't need reminding of how much science has yet to discover and understand, but that doesn't undermine the ability to make an assessment *now*, based on what our current understanding is. Being open to the future goes hand-in-hand with being mindful of the present.