The Nook was a failure because B&N does not have the resources to maintain their own platform. Samsung is probably the only real competitor to Apple here.
However, in the long run, it is likely that open platforms will win. Eventually, the Android ecosystem will get to a point where such software updates stop being a challenge. Then you can just buy a generic Android phone and nearly everything will work. Probably it becomes similar to buying a Windows PC.
You already can buy a generic Android phone, and everything works in it, if the manufacturer is sane.
But you can't get security updates for a long time, except for a few models into which manufacturers or enthusiasts put efforts.
Linux kernel does not have a stable binary interface. Most phone devices (cameras, fingerprint sensors, even video controllers and radio modules have closed-source drivers. You can't expect manufacturers of these parts to update the drivers for their 3-year-old components for a newer kernel: they want to sell this year's parts instead. Reverse-engineering these drivers is tedious, and only buys you a few years on a handful of models.
Long-term support works for Apple because they have essentially one line of phones, with a narrow set of components, and an enormous power over suppliers. So they can afford to buy serious users' loyalty.
However, in the long run, it is likely that open platforms will win. Eventually, the Android ecosystem will get to a point where such software updates stop being a challenge. Then you can just buy a generic Android phone and nearly everything will work. Probably it becomes similar to buying a Windows PC.