I am as far as mission 11, but way before that I was already bored from the repetitive tasks.
Taking out an outpost is as easy as coming in range, equipping your tranquilizer gun (which in other Metal Gear games you would only get further in the game) and shoot every soldier in view. The amount of times I had to use toilets or dumpster to hide is.... zero. The game doesn't force you to be creative one bit!
Also, being able to walk in full sight of the enemy, during the day, just because you are far away enough feels really off. And being able to see enemies though the walls just because you "tagged them" also contributes a lot to the feeling that all in all, there is no challenge.
Was expecting more from a 10 rated game.