Have you played Metro: Exodus? And if so, how does it compare?
Metro's nearly 6 years old now, but sounds like it's cut from the same cloth.
I'm a big fan of both series. Stalker is definitely a lot more hardcore. It's fully open world. The missions that force you more into a linear area are within facilities. Metro Exodus felt less and less open world in every new area you got into.
Stalker will and can kill you every step of the way. You can be running, not paying attention, and run straight into an anomaly that will mess you up. Mutants are really dangerous. The world is alive around you and it's apparently not even working right. I'm curious to see how they fix it because I think it's already working pretty well. But you won't be surprised to just hear a random gun fight nearby you because someone will be walking by and run into a group of mutants. Or maybe it's a group of bandits against a group of stalkers.
Stalker is also a lot more about exploration. You'll constantly find info about stashes hidden around the world. The best ones will have some great weapons. Every nook and cranny is worth exploring. I was going to an objective marker and ran into a train station of sorts along the way. Figured I might as well explore it and found the best assault rifle I've found so far in the game all because I didn't to explore this random train station,
Since everything is so dangerous, the game is very tense. Mutants will really mess you up. You'll die quick to gun fire. Sometimes you'll be in the middle of the woods and in a panic because you can't even see the enemy shooting at you through all the trees and bushes.
The whole game is meant to be pretty realistic in an apocalyptic setting. You're going to die a lot. You're going to lose a lot of fire fights. You're going to die because you get careless and aren't paying enough attention. You move slowly around the world because you need to in order to survive. If you want to rush through a game, you won't like it. But if you can immerse yourself in the world, it's top notch. The Stalker series, whether it's the original 3 or the newest addition, have the best atmosphere in the gaming industry IMO. I'm loving it so far. I've been waiting 15 years for this sequel and it hasn't disappointed. It would be nice if the optimization was better but I fully expected this going in anyway.