Expecting long campaign is a wrong approach to this title. This addition to the series was design specifically to make gamer hungry for more. It's much more than a demo but much too less for a full game.
First off: Kojima did not failed. From graphics through animations and level design: this game is a huge step forward comparing to the previous MGS games. However from the very beginning it's clear that Hideo is going into a different direction this time around. If it's good or not we will find out when full game will come around.
This game is one of not many I have played for long time that let me actually play. I think that, in that terms, only GTA or Saints Row games could be compared to MGS:V. But this game feels much more realistic and open compare to the others. You really can run-and-gun and you can really go stealthy. What I mean by "really"? Well guns feel real, there's strong and well made cover mechanics, you can use vehicles... Basically if you choose to you can find this game quite good action game. But if you more sneaky type, that's good as well. Snake movement is excellent. He goes where you want how you want and that allows tactical approach to the situation.
Ground Zeroes is worth trying. Newcomers will appreciate the graphics, mood, level design and open world. Oldtimers will fill like the first time they played MGS and the guard followed Snakes footstep on the snow. It's a great experience.