Its great as a journey into insanity. Gameplay is utterly mediocre, but once the protagonist starts loosing his mind, there are some many memorable moments. The setpiece with teleporting heavy soldier as lights flicker, shooting yourself in a hallucination, the absolute chaos of final level, the fact that in the end you cant even tell what is real and what is not. Lovely. The absolute strongest emotional moment for me was the epilogue, when the US soldiers come to save you, and I had to fight my own instincts to not shoot at them, because the entire game is about shooting them, it trains you to reflexively do it no questions asked. Brilliant.
However the whole meta-commentary on nature and morality of modern FPS games, and role of a player, fell completely flat. The big shocking white phosphorus moment made me feel absolutely nothing, because the game railroads you into it. Its obviously a bad thing to do, I tried to progress without using it but after like 20 restarts I realized you literally cant, the game wont let you. So then you fire it against your will, and the game points fingers at you and goes "Wow what a horrible person you are, dont you feel bad now?". From what I read original it was meant to be a choice, but during development all of their testers were avoiding picking it, so they just made it mandatory.