I'll keep it short
Skynet captured Kyle Reese and instead of shooting him in the face they put him in a cage and waited for John Connor to rescue him.
Skynet lured John Connor into a trap and instead of having the T-800 shoot him in the face the perfectly logical self-aware computer-based defense system that has control of the nation's nuclear warheads and a infinite number of nye unstoppable robotic soldiers decided that a single unit would do the job hand to hand.
Skynet explained it's plan to Marcus Wright and didn't put anything in his control chip that could stop him from ripping out his control chip.
Nothing at all was accomplished by the end of this movie.
Terribad Editing
Overly narrated everything that happened (pet peeve of mine)
example: We see John Connor telling the resistance via radio to stand down, then at HQ we see them standing down, and then theres someone in the backround to say "They're all standing down because John Connor told them to!"
No fucking way, really? Is that what you just showed me?
Almost every scene had to be narrated and explained no matter how obvious or pointless the event. Target demographic: Stupid people? Made me feel that way anyways.
Too bad, cause it had such potential.
Can't expect too much out of the director of Charle's Angels: Full Throttle