I'm still trying to get my head wrapped around how you think MGSV is justified in wasting the players' time by having their effort to go somewhere wasted .
Open world gives players the choice to explore and subsequently develope their characters, mechanically speaking. Giving players a choice on how they want to arrive to the end game is not a detriment when you have just that...a choice. You can forfeit exploring a good open world at anytime and not be punished for it where those who opt to can find something of value that helps their burden against a challenge later on.
A good open world can and does provide depth when used effeciently to tell new tales to add to the worlds lore which is an added bonus for people who prioritize their experience over the quality of a games mechanics alone. It also helps shape a world that only this medium can tell.
That's just a few. There are plenty examples of masterful open worlds and we do not need to debate what those games are and their quality.
I do think there are plenty of 'me too's that saturate the market and are void of any substance but that doesn't take away from the inherit benefit of such a design. Like anything, it is execution.
Those points are valid if they stand on their own, but how many open world games have actually held a pure focus on a singular one of those elements? Time after time they stretch themselves too thin, discarding gameplay, story depth or environment progression in an attempt to be everything at once.
MGSV succeeds because it has focus. The open world is just a backdrop. You're not actually meant to go into it, even though you have the choice to (if you wandered into the jungle of MGS3 you would just find more jungle and it would be a pointless venture). It's definitely not implemented perfectly - having to walk a long way from helicopter drop points is not ideal. I'd be curious to hear the thought process behind that decision, or if it was simply a concession to the realism of having to do that in actual field missions.
I'm fairly early in Breath of the Wild, but it seems to be succeeding for the same reason. It has relative focus (although the opposite of MGSV's chosen focus), embracing scarcity and making that the theme - based on my brief experiences so far, it's at it weakest when it loses that focus.