Addressing your last point, at least in the UK, therapists usually/often have supervisors. I think it's a fairly peer-to-peer system, rather than hierarchical, once you get to a certain point of seniority.
In Australia it's a registration requirement for a psychologist to have another psychologist who supervises then in respect to the personal impact of caring for their patients.
Therapists and psychologists in the U.S. are required to have supervisors in the latter stages of their training (2-5 years). Many of them continue to have a supervisor afterwards. Most therapists and psychologists are not doctors.