In what way would that have been preferable? By showing these characters meeting for the first time, we are witnessing a significant moment, something exciting and memorable, something we've never seen before. Had we had the full crew on board at the start of the movie, it would have felt like one more Star Trek episode, no different from what we've seen dozens of times before.
Yeah, but Smith wasn't an impersonation - she...was...Kirk!
That just doesn't cut it when you're trying to breathe new life into a franchise that has become so stale, so trite and so absurdly self-referential that people are running from it like scared cats from rising water. Star Trek had become a joke, it had become a laughing-stock, a television fossil, untouched by the evolution of the medium.
As a rule, writers can't bring you back your childhood.
But it's not how they met up; it as some alternate universe take on it. It would've been 'exciting' and 'significant' had it been a prequel and had it been how the characters we know and love actually met up.
Absolutely. This is going to be fun, both for all the new stuff and for the recognizable stuff that will turn up and be used in new ways.
That's a story I would love to see as well. I know there have been novels written about how the original crew came together, but they're not "canon" because that story has never been seen "on screen". I was really looking forward to seeing the origins of the Enterprise crew that I have been a fan of for so many years. Unfortunately, that's not what I got. And given the film's popularity, I suspect that how the original crew found themselves aboard the original Enterprise will be a question left forever unanswered.
Setting an origin story in the universe we are all familiar with would be a creative dead-end in and of itself.
It's not an altered timeline - it's a different universe/reality. Altered timelines that are reset right back are tired and overused, on Trek and elsewhere. But thankfully that's not going to happen in this case - which is a rare situation. I can't think of any other examples of a timeline that is changed and stays changed, or a story that jumps realities and doesn't jump right back. Maybe what they're doing on Lost this season is a variation of one of those ideas but what other TV or movie series has done it?
If you're sticking to the original timeline, you run smack into the foregone-conclusion problem. None of the characters can die, or do anything major - get married, quit Starfleet - that would have been a factor in the original timeline. They'll end up having to do fill-in-the-blank stories covering only trivialities. Why would any writers want to put themselves into a straightjacket like that, when there was another way out?
Yeah, but Smith wasn't an impersonation - she...was...Kirk!
Hers and Shatner's performance are what saves that lackluster episode. As the trapped Kirk, Smith really took on a few of Shatner's mannerisms.
Shatner's performance as a "hysterical woman" was also entertaining, for somewhat different reasons. 
To which "main, true timeline" are you referring? Before or after it was changed by:
