To be fair, it’s not easy to make a big open world that feels immersive and competes with linear games in terms of fidelity (art, rendering, sound, music, etc), even if you know exactly where the player will go and what they’ll do. Trying to then account for every possible permutation of game state and player action is an exponential explosion of work. Without some kind of AI figuring out a believable way for the game to respond in any given situation, your only practical option is to make some assumptions, pick a small set of “golden paths” and polish those.
R* devs work their asses off to an ethically questionable degree as it is, I don’t think it’s fair to imply they’re not making the best possible experience at that scale with the technology available.