Those who denigrate training centres in China as a whole have their own personal reasons for doing so.
Some such critics are not up to the job - they aren't good teachers!
Others dislike working hard - they prefer teaching environments that are not conducive to learning so that they can make a variety of valid excuses to explain away their students' limited progress.
As a rule, talented teachers of EFL who enjoy working hard can make high pay by working for training centres teaching wealthy Chinese and their offspring. In contrast, either incompetent teachers or those who like to idle along at work will be shown the door by a training centre after a week or two. However, all is not lost - they can enter the public sector instead. But their classes will probably be too big. No matter, their foreign faces can still make easy money, though it's much less than what training centres pay their hard-working and versatile foreign teachers!