Disappointing third act

Rating: Null/10 (20 October 1999)

The first and second acts are amazing. So good, in fact, that they almost make up for the misguided wrong-turn the film takes later on. Go see it and judge for yourself. NOTE: THIS ANALYSIS CONTAINS SPOILERS.
The first two thirds of the film are breathtaking - elegantly written voiceover, dark yet hilarious exposition, well-drawn characters, and beautiful directing. Not only does Fincher know how to convey the perfect tone of the film, but also every frame is like a wonderfully crafted piece of art. Why can't all directors be like David Fincher?

You can't fault him with the film's wrong turn. That blame lies with the script. What we have are two separate concepts:
1) Tyler and Jack fight to experience life, prompting a whole group of disenfranchised men to join up with them. Tyler becomes a hero to the men, utilizing them as his personal army of revenge against all that is wrong with society. But Tyler starts to go too far, and Jack must stop him.
2) Jack discovers that "Tyler" is his other personality. Through "Tyler" Jack has achieved hero status to practically an entire generation of young men. But the "Tyler" part of his personality has laid plans for a massive act of destruction, and Jack is unable stop "himself" from committing this act.
Both are great concepts, but they don't work together. The reason other men join the fight club is because they see Tyler and Jack FIGHTING. This is the entire basis of the concept. But Tyler and Jack are the same person, right? So are the men watching Jack beat himself up? Seeing a man punch himself might incite a few laughs, but it would hardly prompt a group of men to join a radical and violent organization and regard this man as their leader. Is this nitpicking? Am I wrong?
The film would have been better off keeping the whole Tyler/Jack thing as subtext. Instead we get an ending in which Jack shoots himself in the head, causing "Tyler"'s death. But then Jack survives, and yet "Tyler" is still dead? Huh? Are we supposed to put any kind of emotional stake in these confusing events? The whole thing ends up ruining what could've been an otherwise near-perfect film.