Brook isn't immune to criticism. He didn't always dedicate himself to training. He's the most talented boxer I've seen in terms of variety of punch. He always lacked a bit of power which probably, coupled with a lack of dedication earlier in his career, prevented him from winning more than one world title. He will definitely have regrets in his career. He was also a bit unlucky that he wasn't quite the right weight at the right time, hence going up in weight to fight Golovkin simply to try and make a name for himself.