Which part? Hard to have a discussion without specifics.
Many psychologists who belong to different schools of thought – e.g. CBT, positive psychology – don't agree those practices are helpful and don't agree with their theoretical underpinnings
There is a lack of high quality empirical evidence for both the safety and efficacy of the kinds of practices you advocate, and also for the theories which motivate them. By contrast, more mainstream approaches such as CBT have significantly better empirical support