Why? Because until the last half hour or so, I could ignore all the "CinemaSin" type problems because the movie was fulfilling it primary function -- being a fun summer movie. Then, with about 30 or so miniutes left, it's like the "Boys (and I mean boys) in the C Suite" phoned down and said: "Hey, this is a big summer block buster and we're releasing it in 3D as well. We want you to change the ending so it makes absolutely zero sense, but gives us a huge space battle."
"But that makes no sense, and everyone has already seen a big space battle ending for the last two movies. Couldn't we have an intelligent ending."
"No. And we want you to throw in some stupid sexist guy jokes."
"Yes. Have Scotty suddenly not able to respect Jeanine and have something blow up so he has to let her fix things."
"Why the heck would he do that?"
"Because we think it's funny."
"[low voice] @#$! [regular voice] Anything else?"
"Yeah, we want the villain to be a crazy Star Fleet vet who can't deal with the Federation being at peace. Sends a strong anti-war message."
"You know we used that last time, right? Crazy Admiral dude who wanted to use Kahn to justify a military build up."
"Yeah, well, do it again!"
"And we want a big fight over a futuristic city."
"You know we did that last time also."
"It makes even less sense this time!"
"Just make it happen."