The problem is not the current size of the universe is big, it is that it is expanding with time. Aliens will still have to contend with the same physics laws b

The problem is not the current size of the universe is big, it is that it is expanding with time. Aliens will still have to contend with the same physics laws because they are universal (in the tight meaning of universal here). We can actually model the recession velocity of emitted photon from a source (will be higher that speed of light) depending on our universe model. To have aliens that are near enough so that they made contact with us ( through some signal not by abduction of humans) would mean they they very close on cosmological scale that they must be living within our detection capabilites. And with all our searches for life so far nearby we couldn't see a signal for unique civilization signature.