Honestly, this game just seems pointless. It completely fails to explain the one thing that is sets out to (How Big Boss became evil), and it feels like the only real explanation that this game provides to BB's story is a plot-hole from the MSX games that no one even gave a shit about. So the plot's largely self-contained, and there's nothing wrong with that; MGS3 was largely self contained too, at least when it first came out, and that's one of my favourite games of all time, so what gives? Well, MGS3 actually had a good plot. MGSV... not so much, and I think a good part of that is because it's so sparsely placed. The games 'main missions', and I do feel the need to say that in quotes, are so rarely important, you could easily skip straight through half of them, and that's not even including the hard mode re-do's. It feels like a TV show that's 70% filler, and not even the good kind of filler that explains characters in more detail and expands on sub-plots that aren't in the main plot's scope, but the bad kind of filler, where it's just the main characters doing stuff with barely any context, the kind that you can just skip past on the DVD box set (Or, the Netflix stream? Amazon Prime digital download?... Hulu? I don't know what people do anymore), and lose nothing. Then, season two comes around, and there's a pretty good arc going on, but then they forget to finish it, take a season hiatus, and just play re-runs for the majority of the season, re-runs of filler, keep in mind, and then at the series finale they just do an, admittedly cool, two-parter, and then kill all the fan-favourite characters for shock value, and then throw in a random twist at the end for no real reason.
TL;DR, The story isn't that good, but how is the gameplay? Well, amazing, to put it shortly. All the mechanics are great, and the freedom to cut infiltrate what you will is done very well, and it's a bar-setter, not only for stealth games, but maybe games in general, but I'm not a particularly huge fan of the open-world gameplay. It's well designed, to be sure, not as content-dry as something like Skyward Sword, while not being bogged down in collectibles like in the Assassin's Creed series, but my main problem is that it doesn't feel like I'm accomplishing anything; outposts that I 'capture are filled back up like that, and while putting too many worthless things is bad in an open-world game, MGSV has very little that feels worthwhile; the open-world just feels like a bother, though that might just be my overall distaste for open-world games.