So here is an example from two different games that I feel illustrate my point.
Star Citizen, has NPCs which wonder around stations and landing zones, there is no NPC ship traffic outside of NPC mission targets. The NPCs in game often bug out and stand in chairs, t-posing or glitched halfway in the floor or wall. They don't add to the feeling of life, if anything they make it feel more like you are alone. Silent idiotic clones that mindlessly roam around.
Elite Dangerous. Has NPC ships and soon NPCs walking around in stations. They follow pretty scripted routines and are mostly silent. They are a fair bit easier to figure out than players when online but they are not all that life like. They are more like borg drones that silently go about their task. The NPCs in missions are ok definitely better than Star Citizen but they are still pretty easy to tell from an actual person.
I can also tell you both of those games have dedicated years of code work in getting those NPCs working as well as they do now.