Well, I guess the problem was that the first Star Trek 'reboot' was very very good and a hard act to follow. This one is nowhere hear as good and seems to have been written to a rather restricted formula, probably by a committee. The wonderful inventiveness and cheeky wit of the previous movie have here been subsumed into a rather desperate nudge nudge wink wink that means there are no plot surprises, since the twists are clearly signalled well in advance, and (never thought I'd hear myself saying this!) the movie is a re-tread of the 1982 Star Trek II Wrath of Khan, only not as good. They literally took Spock's death scene out of that movie (spoiler alert, I know) and re-ran it with Kirk. So someone decided to simply raid the old Star Trek canon for plots that audiences used to like, and serve them with a couple of changes. Surely the whole point of the wonderfully iconoclastic let's-blow-up-history plot of the previous movie was that they didn't HAVE to stick to the canon any more but could be genuinely creative? The suits must have felt too nervous about bankrolling something actually new.
Benedict Cumberbatch was a surprisingly uncharismatic baddie, and it was appallingly violent in a way that made it difficult to retain one's sympathy for the 'good' guys. I can't imagine that this is going to generate the crucial repeat business that the previous movie did, and may signal doom for the franchise - I understand the US box office has been disappointing and the film hasn't broken even yet.