[Alex]

It isn't that the time travel stuff doesn't make sense. As far as such goes it was handled pretty well (though it isn't explained why sometimes the Red Matter black holes create time portals and other times it just destroys everything (unless Vulcan -- and Nero once again -- have simply been shipped to another time).

It is the rest of the story that is stupid: the fact that Spock alone was trying to save Romulus, that a mining ship is super armed and powerful, that once in the past Nero spends 25 years waiting for Spock so he can exact revenge rather than going to the still existing Romulus and beginning the process of saving it, that the entire Federation fleet is in the Lawrentian system but whatever the reason for that is, it goes unmentioned, that despite this there are a dozen uncrewed ships including the new flagship vessel just waiting to be crewed by the entire student population of Starfleet Academy, that Vulcan and Earth apparently have zero dedicated defences other than starships and yet still sent their entire fleet to one system off somewhere else, that Vulcan is just 8 minutes away from earth, that the entire idea of a spaceship is rendered obsolete by the super-teleportation deus ex machinaed into existence by Spock Prime. That even though Vulcan was about 8 minutes from Earth (or some ridiculously small number given by Checkhov in his shipwide mission briefing) Earth was at least a few hours from Vulcan (since that is how long it took the Enterprise to get back), that a moon orbiting Vulcan is somehow an isolated Federation outpost manned not by Vulcans but by a lone super-genius engineer and his own personal Muffit, that Nero put Spock on that moon rather than letting him watch from the Death Star so he could gloat, that a device that destroys through black holes apparently requires first digging a hole to the center of the object since a black hole simply put on the surface apparently wouldn't be destructive enough (and one wonders how exactly Spock was going to dig a hole to the center of a star so that he could save Romulus), that apparently Romulan miners like to keep their ship decks under several inches of water, that when an Academy cadet is particularly brave he will be given command of the flagship vessel of the fleet.

Compared to everything else the time travel and its implications was a paragon of reality and clarity. But it was a fun ride. A stupid ride with characters I am very fond of, but a fun one.