The problem with the BNO passport is that no-one respects it. Not even the British government, which requires BNO pp holders to line up at the queue for foreign (non-British) passport holders at UK border control. And certainly not the Chinese government.
Many countries are not familiar with it at all, so in some cases will either mistakenly treat it favorably as if it was a BC passport; or at the other extreme even suspect it of being a counterfeit - in one reported case, even the local British Consulate wrongly 'verified' a BNO passport as being a fake British passport.
Leaving aside the exorbitiant fee, it's no wonder that the vast majority of people with BNO status have failed to renew it. Most BNOs are Chinese citizens and use the HKSAR pp instead which is much cheaper and has similar visa privileges (or lack of) as the BNO. Those BNO holders who are not Chinese citizens and hold no other nationality are now entitled to full British Citizenship following recent changes in UK nationality law.