Well, that is a major problem with clinical psychology isn't it. It is a very diverse field, with dozens of theoretical approaches, each of which vary in their ability to produce specific effects during intervention. Most types of therapies have common factors, such as building rapport, problem solving, self reflection, positive regard for the client etc, which help to promote positive change. Therapies and approaches vary however in their ability to go beyond those common effects and treat the specific symtoms associated with a specific presentation. For instance, behavioral psychologists and psychoanalysts might both develop a validating, warm relationship with their client, but in treating a specific anxiety symptom, behaviorists would likely use a form of exposure therapy, while a psychoanalyst might be more concerned with interpreting your dream and the relationship you had with your mom. Those specific differences in how you treat clients are important, because one actually addresses the problem and has empirical support/evidence for being effective, while the other does not.

Point being, there are many 'accepted' therapies within the field of psychology that are probably as wrong headed as reiki. This is then complicated by the practitioners skill. Effective therapies can be carried out poorly, and have no real effect. People using bad techniques can still be highly skilled at promoting those common factors that promote change, and be effective. This is then further complicated by the clients specific presentation, personality, and context, all of which can effect treatment in positive or negative ways.

This stuff is complicated, and I'm certainly no expert, but the take home message I think is that you shouldn't dismiss all of psychology and turn to improbable therapies based upon poor past outcomes or experience. If accepted therapies have not worked for you, it does not make alternative therapies more or less valid, those are seperate issues. The field is diverse, and it will take some effort on the clients part to be selective about what kind psychologist they see, and be knowledgable and skeptical about what they're buying.

All the best