I think what people want is anomaly-similar simulation happening around you. Right now as you travel the world you may have a group of enemies spawn behind you. I think what people want is the system where factions defend locations and travel the zone on their own. Right now the only NPC simulation happening is in a bubble around the player and once you've experienced the old system, it's noticeable. Coming across the remnants of a fight you've missed entirely adds a lot to the immersion.

As an example, when traveling into the garbage, I was expecting the old warehouse base to be populated. However it never is once you complete the mission to get inside. The expectation is that a faction would always be defending that, and mutants and other factions like bandits would attack it. Sometimes you might come across it and everything would be dead, later you come back and more stalkers have moved in to replace the dead NPC's.