What makes a game's world "feel alive"?

I want to preface my question by saying that I do not like open world games, but I think its fun to read about people enjoying things like RDR2, Cyberpunk, Skyrim, etc.

However a common criticism I see is that for some games the world does not feel "alive", and that never makes sense to me. If I walk around in the real world, nobody will ever talk to me or offer a quest or anything, but if there is nothing to ever do, then that is boring as well. What are people asking for to make these worlds "feel alive"?