Okay, so it's probably not giving away anything drastic to say that everything leads to a confrontation between that which controls the robots and our main characters. That what ensues is primarily dialogue may strike some as disappointing, but that's not really the issue. What is said is frequently funny, but it also suddenly becomes as didactically libertarian as Elysium was PC-liberal. (I'm equal opportunity in my dislike of preachiness.) Not knowing Wright's politics one way or the other, I half think that he borrowed a classic metaphor without thinking it through - the Body Snatchers, which these robots essentially are, were originally a metaphor for communism. They've been updated through the years to represent different kinds of conformity (Abel Ferrara made them a dig at the military, for example), but one thing remained consistent - they've always stood in for a kind of conformity the director himself felt truly opposed to.
So even as we may cheer that yay, our heroes are fighting back conformity, you have to ask precisely what that conformity is - and in this case, it's maturity! The one thing all Gary's friends have correctly been telling him he needs to get some of. There's nothing wrong with a contrarian position here - if you want to insist that being a drunk is more awesome than being a responsible family man, go for it. But this script doesn't do that. In wanting to have Gary be right but for the wrong reasons, it kinda-sorta cops out...
Except then, in the last five minutes, the movie takes a drastic lurch into almost a completely different genre, to the point that it feels like somebody told Wright there was a ton of money left over, he could do whatever he wanted, and he simply said, "Let's throw in cool shit we come up with on the spot." You can argue that in its convoluted way, it does make Gary thoroughly wrong...but you could probably argue the opposite as well, because it's such an insane turn that putting too much thought into it is pointless, and it's tough to reconcile with everything that's come before. Chopping off these last few scenes would make the movie 100% better - or at least making them into a single throwaway gag shot rather than an entire new tangent.
It is fitting, in a way, that the movie can't let go of its own geekiness long enough to give us a properly developed conclusion - like Gary's life, it peaked early and can't quite grow up in the end.