From a capitalist point of view, Neuralink will only become profitable and valuable if they go full sci-fi and offer a brain/computer interface that anyone can use, AND that there's systems and applications that use it, AND that it becomes popular and "better" than e.g. smartphones.

But that last one is the kicker. AR never became mainstream. Unless a brain interface is faster and more intuitive than e.g. a physical keyboard, it will never become mainstream either.