Congrats are definitely in order for Hideo Kojima and his team for earning such critical acclaim once again. It appears that his role in Metal Gear will be ending on the highest of notes, and that's great for him.
That said, despite the superlative reviews, I'm sitting this one out. Open-world games and I never mix, and I've wasted far too much money on other critically-acclaimed open-world games just to wind up getting bored with them after a few hours and inevitably trading them away within a week. (GTA games, Oblivion, Skyrim, Saints Row games, Fallout, etc)
I have, in my own mind, a preferred formula for games. I prefer strongly scripted, more linear experiences that keep me focused and moving forward. There can be some room for exploration, but if there's no driving force to keep me playing... I get bored with side activities, lose interest in the main storyline, and just stop playing. I get that my preferred formula for gaming is gradually being replaced by the open-world/sandbox model, but I'm not personally a fan of this direction.
That said, creators have their own vision when it comes to game development... and I don't have to like it or buy it to respect it. If this is Kojima's vision, good on him for seeing it through. Sure, I'm disappointed that there's a mainline MGS game that I won't buy/play, but life goes on. It's obvious that reviewers love it, and I'm sure it'll be a hit. I'll stick with the more linear games and enjoy those.