It's not "old" continuity, it's the continuity. The one and only in Trek. One cancelled Trek show doesn't mean the end of that original continuity, which, after all, is where Star Trek shows and films were set during their 40+ years existence. AbramsTrek does not represent any norm or standard for Trek. It's one thing to make a summer popcorn flick for the masses, and it's a completely another thing to make a permanent TV show. Yes, the original Trek continuity also lives on in books etc., but it will certainly continue in a new Trek show once it's made in the future. But first we have to say au revoir to Abr-Kur-Orc.
It was more than one cancelled series - it was a steady decline in ratings and intrest since The Next Generation
ended. There are ratings charts on wikipedia, movie box office details etc.
As Star Trek
(as well as all the other reboots out there) have proved is that people care more about characters than continuity. Seeing Kirk and Spock in their prime once again, out saving the galaxy, is far more awesome than the adventures of Captain Nobody in the 25th century.
Besides - who says Trek has been one continuity these past 45 years? Even discounting many excellent novels and comics that went in different directions to the movies and TV series', every incarnation of Trek has been declared uncanon by righteous fans at one time or another. The animated Trek, STV and Enterprise get it the worst. But take a look at the videos in my sig, and then try to explain how The Original Series and Voyager can be part of the same Trek universe. Or Deep Space Nine and TNG. They all imagine the Trek universe slightly differently, and it's only a huge dollop of willing suspension of disbelief that keeps it together.