It definitely has major issues and as a final product it feels sorta fucked.
Pros:
Enemy AI is excellent and variable, super AI or AI that can't be played around with tanks a stealth game.
Tranqs have been nerfed significantly. I love MGS3, but the tranq pistol ruins all difficulty when it comes to sneaking around. In MGS V, unless you constantly request supply drops, you can't skate by via tranqing nearly as much as previous MGS games.
Stealth is perfect for an open environment. The options you're allowed to turn off are fair and makes the game more challenging. Enemy sightlines are far but its easy to know when someone sees you. Hiding after being spotted or going into alert mode is a great mix of moving and waiting. Sneaking around and not getting caught feels really, really good.
Gameplay options decided upon by the player. You can completely fuck up a mission in your own unique way and figure out how to salvage your mistakes. Tons of options when it comes to infiltration, tons of options when it comes to combat. Very rarely does it feel like something is wasted when it comes to gameplay options.
Cassette tapes are pretty damn good. Fantastic performances from everyone on those. Huey being a monster, really welcoming to see a Emmerich be a complete and utter fuck up.
Great licensed music.
Cons:
Repetitive side ops, way too many. Halving the amount of side ops, making each one more unique, and upping how much GMP you get for each side op would've gone a long way.
Plot is bare bones as fuck, storytelling is fine/good. Almost nothing happens in MGS V, every other MGS it feels like there are high stakes for someone or something, shit is going down and you're in the middle of it. In MGS V, a handful of events occur and some of them don't matter more than five minutes.
It doesn't feel like the 80's. You could tell people this takes place in 2015 and everything would make sense besides the Walkman and reliance on cassettes. Ball was dropped really hard here.
Around 35 unique main missions, the rest are repeats, some of the repeats are neat at least. If the lack of plot seems fucked up, the fact that Kojima and his team couldn't make enough story missions to connect the plot with gameplay is telling. Something went wrong in the middle of development.
Characters are more interesting in tapes than in cutscenes. Bringing back characters for almost no reason and/or making past characters kid masterminds. New Metal Gear was simply alright.
What we got is a great game, but what we weren't given will always be a bummer mystery. Something happened while this was being baked in the oven, and it clearly fucked up the baking process.