The first time I entered Valentine, I spent several hours just walking around, saying hello to people, eating, drinking, taking in the atmosphere. It was an incredible experience.
Rockstar always made highly impressive, realistic feeling worlds, but it always felt more appropiate to just tear it all down and mess around with the guns and whatnot. But RDR 2 made me feel the opposite, I just wanted to appreciate the world as is. Kingdom Come Deliverance felt very similiar to this. Much clunkier, buggier and lower budget, but one thing I adored about that game was, well, this. The commitment it had to immersion. As soon as I finished KCD, I started wondering what a higher budget take on this would be like. And a few months later, RDR 2 came out...
And it's not just window dressing. You can actually interact with the world. NPC's react to your antics, you can defuse/instigate situations, say howdy, hunt, play a bunch of minigames, etc. It's a great contrast to many open worlds out there that while look great, are still feeling static.
One of my other fav games of this gen (Witcher 3) really highlights this point. Because I think TW3 came pretty close to Rockstar's level of quality in the world layout and visuals (Novigrad is such a fantastic city) but it didn't even allow me to sit down at the tavern to take in the atmosphere. Even drinks you bought were just treated as regular loot, no animation for drinking. There was only 1 minigame (gwent) and even that sent you on a seperate screen altogether. Now one might argue that RDR2's "animate everything" approach can cause tedium, but when it comes to this sort of "immersive" fluff, it adds A LOT to the atmosphere, at least for me.