There's a scene later on in the film where he clearly explains his (predictable) modus operandi to Andrew: Fletcher believes great musicians can only be forged in a crucible of fear and torment, and says he’s just trying to get the best out of the best.That's perhaps where the problem lies for the movie’s critics.
"We're supposed to leave our seats feeling just a little admiration for Fletcher and his alleged standards, because perversely, they really do tease out some greatness in Andrew," Stephanie Zacharek wrote in To others, the implications of the final scene’s triumphant tone were less disturbing and instead flat-out comedic. I may not be wrong in thinking that Jazz would be one of the few genres in music that is able to encompass such a diverse range in tempos, from soulful pining numbers to even eclectically charged dance numbers.
However, with a steelier resolve, he returns to the stage, and interrupts Fletcher in the middle of his speech by playing ‘Caravan’, eventually cueing the band in.The two share looks of disapproval over each other’s actions, but as Andrew pushes himself and his performance progresses, Fletcher seems to warm up to him owing to the visible dedication Andrew was putting in and an incredible performance, and begins to guide the band. It is clear that in his pursuit of becoming a great musician, he held Fletcher at a very high regard, and that his approval would matter a lot for him. As much as we've regarded Fletcher with horror throughout the movie, Andrew's ultimate achievement is that he finally impresses him, without caveat.