I think going in with the thinking that this is going to be some epic finale for the franchise, or is the swansong of the franchise, is going to lead to disappointment. It's not really that game. That was MGS4, for better or for worse. The story in this game isn't necessarily bad, and I'll certainly take it over the character assassination of Solid Snake present in MGS4 (one of the main reasons why I hate that particular game), but it's not like there's a whole lot here. The truth is, all of this extra content detailing the exact nature of Big Boss's journey is superfluous.
I feel MGS3 alone was good enough, and it would've been great to just have that. It's nice to leave things to the imagination sometimes, and I feel this whole journey is a testament to that. MGSV's story kind of feels unfinished if someone tries to take it as some kind of conclusion, because it's not. Not necessarily in the sense that there's a lot more to tell, but just that it's not a conclusion to the saga. And it's not necessarily a good way to bring things full circle since it doesn't really do that in some great way either.
Basically, it's a story in the life of Big Boss. That's about it. It really doesn't do anything thematically important for Big Boss's journey nor does it provide some greater understanding of his character that we didn't already have. So superfluous I feel is the best way to describe it. That doesn't mean it's bad, but in a game which is probably 2-3 times longer than the previous main entry, there really isn't that much there, and the crappy pacing kind of hinders it in that sense.
I think MGS5 is a game that gets a lot right, and a lot wrong. And how much you like it is going to depend on the type of design you like in games, and what made you a fan of the franchise. It really does kind of jump to the other end of the spectrum in comparison to MGS4.
With MGS4, I feel if there had been a better balance in the game design, it really could've been something special (even though I hated that story). With MGS5, I don't really think that way. I don't dislike it more than MGS4, but MGS4's disappointment for me was because it really could've become something far greater than what it was. Even if you were to rectify some of the issues I have with MGS5, I don't think it could become that, since you'd have to pretty much overhaul it. Then you basically have a different game.
Plus, I was kind of blindsided by the length of this game. I really didn't expect that. That's a backfire of a blackout I guess. Although I likely would've enjoyed it far more if the pacing wasn't the way it was. It does get very repetitive.
Still, though. Seven years for this. Kind of sucks really to feel this way.