A therapist is like a personal trainer. There are lots, not all are good. For those that are good, they can only help
you if you put into practice and develop the skills yourself. That second part - which you omitted mentioning - is vital.
No amount of bad eating can outdo to benefit a good trainer can provider. And a bad trainer will just as often put people off of trainers and lead to the bias that "all trainers suck" overgeneralization.
Similarly, bad therapists exist, and lead many to the same "all therapists suck" overgeneralization. Those who have had a good therapist know it is life-changing. More than is realized, though, is that many of the "bad" therapists have non-compliant, non-individual effort patients.
I've seen first hand the value a good therapist provides for a cooperative patient. I've also seen how that same therapist had a poorly compliant patient who declared the therapist was garbage. In reality, the patient's effort was garbage. I've also seen therapists that completely miss the boat and fail to help people.