Good film but some problems prevent it being a classic (some spoilers)

Rating: 7/10 (1 October 2012)

First of all I want to make it clear that in my opinion this is a good film and people should see it. However I don't think it is a 5/5 star film "the new Matrix" or whatever, there is too much hyperbole surrounding it.
I simply don't think the film is as good as Brick, the previous Johnson/Gordon-Levitt film, and not as good in terms of delivery as Twelve Monkeys.
So the positives are great acting, a good premise, a good opening act, some great shots and the future city/society looks pretty convincing ('vagabonds' everywhere, social decline, rampant crime and violence, a drug fueled elite partying it up in strip clubs whilst millions go hungry outside... hey, this maybe is the present?!). Willis is good in the role, and there are some great one liners peppered throughout the film.
And I also don't think the time travel premise is the problem. Too many reviewers on IMDb are complaining about the time paradoxes and the plot holes - hold on everyone, it is a time travel movie, they will always have some level of paradox in them because time travel is always paradoxical. Anyone who thinks you can make a 'perfect' time travel movie has yet to show how it can be practically done, since every instance of time travel creates an alternative world anyway. Only the Canadian TV show Continuum really deals with this issue by leaving the question about whether the time travel has already happened ambiguous (i.e. has the future world already been created by the act of traveling back in time, in which case the show can become utterly deterministic since it has 'already happened'). Anyway I digress, don't get too bothered about time travel based plat holes, what stops the movie being a classic is a question of how it was delivered, not its sci fi credentials.
For me the movie was not engaging enough for its length. It dragged from the middle onwards because it relocated the action from the gritty, grim dystopian city to a farmhouse which looked like it could have been in a movie from the 1950s. Johnson should have stuck with the tone and pacing of the first half more closely, because then the movie spins off into another film about a boy with powerful psychic abilities and a moral dilemma about whether he will grow up to become the supreme baddie or not. Willis thinks so, Gordon-Levitt believes that we can make our own fate and the child can grow up to be good, but this moral story line is grafted onto the previous one about fighting your future self. That for me was the core of the film, the second act pretty much neglects it in favour of some farmyard based children of the corn/village of the damned action.
And the problem was tone, we went from city to countryside, different mood, colours and pacing and it slowed everything down. Willis' quest to kill the boy before he becomes some major baddie was a bad idea, it was a story too far and it meant that it included a load of stuff about telekinesis which is crucial to the plot but was not integrated into the story in any meaningful way. Then it becomes a story about time travel and telekinesis but without exploring one or the other that well.
My contribution to how to make the film better would have focused on the time travel aspects a bit more. The most gruesome bit in the film is when they track down another escaped target from the future by carving up his younger self, as they do so the future guys body starts to disappear, his fingers, nose, legs and so on. That was gripping body horror stuff which could have been done effectively at the end. Imagine Willis and Gordon-Levitt squaring off against each other, totally outmatched (like Dekkard and the Replicant at the end of Blade Runner) and the younger version has to break his own fingers or shoot his hand off to stop Willis from killing him - it could have taken place in a disused warehouse or similar dystopian trope. Been done before? Maybe, but the tension between the younger and older version and the cat and mouse game between them could have made a much more impressive story.