They could have pivoted to Android earlier. I had a BlackBerry Q10 and their BB10(QNX) was actually pretty good (the unified messaging was amazing at the time), but it was clear even then that without proper Android app/ecosystem support, it was always doomed to struggle. (their clever emulator was great, but wasn't enough). - https://www.youtube.com/watch?v=JXewkl5K7-M
When they finally did pivot to Android, their phones were pretty good (I carried the "BB Priv" for a long time, and the KeyOne was great from my short time with it). But they were way too late by then, and had to face the onslaught of Samsung / LG competition, who all had newer tech at cheaper pricing.
A BlackBerry Priv in 2011 might have saved the company, it would be competing against a "Droid Razr" and an iPhone 4S. The Priv actually arrived in 2015, and was competing against a Galaxy S6 Edge and iPhone 6S Plus. It was way too late -- people who loved their keyboards had already learned to survive with "phablet"-sized smartphones for a few years by then.