I always saw the ending as the statement of the film; it's not for anyone else to set the boundaries about what you're allowed to prioritise as long as you can live with the outcomes.
He cut off relationships, he destroyed his body, he sacrificed his sanity and he fucked up his career, but he was doing all that for the sake of appeasing Fletcher and meeting his rigorous standards.
All the while he's doing his Fletcher sees him as another mewling student looking for validation, and treats him like shit because of his lack of agency and his sensation that his ability alone makes him special.
Once Andrew behaves with agency, Fletcher responds positively to his existence.
He's rewarded not for chasing the validation of Fletcher, but finding it within himself and pushing it into the world. I took that as the film saying the validation of that kind of single minded pursuit can only come from within.