Problem is you’ve got 28 seasons of TV show and 10 movies setting up all kinds of races and people and historical elements, accidentally make a reference to the wrong person in the wrong time and the canonheads get their panties in a twist (again Enterprise). Even the mirror universe has a bunch of canon having appeared in 9 episodes spanning 3 shows. All the reboot is doing is snapping off all the other stuff and giving the a clean slate to play with, now they don’t need to worry if they’re not supposed to meet that race yet or have warp too fast. Reboots (and their cousin ret-cons) are pretty common place, and something Trek should have done a LONG time ago. Problem of course is there’s this chunk of the Trek fanbase that’s obsessive on those things to the point of complaining to the stars about buttons changing function, so they always had fear. Which is sad, because originally Trek had no canon, and it worked better that way, http://www.postmodernbarney.com/author/john/ (weird archive, read from bottom up).
I understand that some aspect of the Mirroe Universe and other races have been touched on. Still, they are not fleshed-out to the point that they cannot be tweaked or expanded. I agree with an earlier poster on that Abrams seems to want it to both ways. Personally, my opinion is pick one, dude. A complete “reboot” or a remake - pick one. Hell’s bells, they could have just tried an entirely new storyline with new characters within the broader universe - good writers would find a way to make it work. Heck, even go the AVP route and have Gorns versus Tholians! ;-). Instead, it seems as though the writers chose the lazy route - take accepted characters and change things just enough to give the appearance of orginality but with damned little truly fresh.
A good example of how to deal with years of Canon is what ‘Doctor Who’ has done...use what you works and ignore the rest...there is always a tie to tie things together later if needed.