The issue for me is that challenge/reward isn’t balanced properly to be fun and engaging throughout, there’s often little rampup in difficulty or loads of tedious side content that only detracts from the experience.
Sometimes it can work but it’s really got to be a world/gameplay where just spending time is rewarding itself, can’t think of much beyond Zelda and MGSV really.
It’s why I have no real hype for Red Dead 2.