It is quite possible that life is only just reaching the technological stage everywhere, since it has taken quite a long time on this planet, and we know that life can probably only form around second generation stars like ours, so it probably did not form in the early universe, so that all life therefore started everywhere only in the last few billion years. It is also possible that there is a yet to be discovered, (by us) doomsday technology, which can not ever be foreseen by it discoverers, but which always destroys the species which discovers it, and therefore technological species are just short lived anomalies. And lastly the difficulties of traveling across the vast distances of space are so great that it seems likely that we will never do it, unless we discover as yet to be even imagined new and probably impossible technologies, and therefore given that intelligent life is almost certainly very rare, it is most likely that no two life forms from different star systems will ever meet before their stars die, anywhere ever, even though across the univers there may be millions of them..

If they were nearby, they would have built a wall around the Earth...

If we find them, then we would probably be more advanced, unless they've been hiding from us. If they find us, then they would probably be more advanced.

If there is life on another planet, similar to ours, they'd be wise to keep their
presence secret to us.
We ruin everything we touch.
They'd be much better off not having any contact with us.