Marketing
BB10 is good as anyone who has used it can attest to.
BlackBerry has a marketing problem. It's not a problem with the core product. Young kids think BB is for old rich technologically perhistoric white business people. It's not a cool image to have. And the old rich white people think BB is dead so they buy iPhones anyways. All that's left is people who know what they want and don't care what people think because they know it's better. That's an incredibly small niche to serve.
They didn't do enough to inform people that BB10 was completely different than BB7. The public perception is that they are one and the same. Quite frankly keeping the legacy name hurt them. The new OS needed to be called something different and it needed a bigger marketing push. If they had stuck with the name "QNX," that would have served them better. BB Z30 running QNX. They need to call the OS something new, something alluring, and something that sounds cool. That way people cannot mistake that "BlackBerry is dead" or say "they still have those?" Instead of being on the defensive, users can point and say "QNX is the new hot shit, are you seriously still using an Andriod or iPhone?" The OS really is better in many, many, many ways. Unfortunately the name BlackBerry has too much legacy baggage.
I found refuge with BB10 after my N9 crapped out so I'm not a fully fledged fanboi and I've never even used BB7. Nokia left a big gap in the market and BB did not target those users at all. That should have been their new base for QNX.