I had a long conversation with their engineering people way back before BB10 came out. At the time you had to apply to get access to the full blackberry SDK, and IIRC you also had to sign an NDA. Meanwhile Android and iOS were in full swing and wouldn't you know it, the platforms that had better developer experience, that prioritized making it easy to write apps, were successful.
Blackberry is just institutionally incapable of handling this sort of relationship with the community. It's that legacy telco "us vs them" mindset at the top of the org, and it filters down whether implicitly or explicitly.