But that's part of what makes traveling in real life a chore. If I could drive anywhere I wanted and show up to work whenever, I would be more likely to enjoy the ride
Practical =/= Fun
If mountain paths are too restricting, everyone will simply use fast travel after the first time they see them. People like open worlds, but there's a reason "backtracking" has a negative connotation.
I mean, open world or not, if there's a mountain in total wilderness, somewhere very dangerous, you bet there won't be 10 000 paths to climb up. It's part of an open world game.
And personally, I love backtracking. It gives me a sense of place in a game. If you never backtrack, I might feel like following a corridor instead of being somewhere important. But that's out of topic.