Current education and training in psychological interventions is mostly based on different ‘schools’ (traditions such as cognitive–behavioural or psychodynamic therapy), and strong identification with these specific traditions continuously hinders a scientifically based development of psychotherapy. This review is selective rather than systematic and comprehensive. In addition to the consideration of other influential publications, we relied on a literature search in Web of Science using the following terms (update: 24 December 2020): (psychotherapy AND meta-analy* AND competence*). After summarising current problems, a pathway for solving these problems is presented. First, we have to recategorise psychological interventions according to the mechanisms and subgoals that are addressed. The interventions can be classified according to the foci: (1) skills acquisition (eg, communication, emotion regulation, mentalisation); (2) working with relationship patterns and using the therapeutic relationship to modify them; and (3) clarification of motives and goals. Afterwards, the training of psychotherapists can switch from focusing on one theoretical framework to learning the different competences for modification according to these new categories. The selection of topics to be addressed should follow best evidence-based mechanisms and processes of mental disorders and interventions. Psychology offers knowledge about these mechanisms that can be understood as a basic science for psychological treatments in general. This requires better connection with basic science, new research efforts that focus on treatment subgoals, theory-overarching optimisation of the selection and personalisation of treatments, and new types of training for psychotherapists that are designed to optimise therapists’ competences accordingly, instead of limiting training programmes to one single theoretical framework.