I think part of the reason therapy is more difficult than seeing a doctor is because working on mental health can be so much more complicated than getting a more physical thing treated. We don't really have medicines that are nearly as effective for mental health issues than for physical health issues, and unlike other surgeries, lobotomies really didn't work out that great.

Because mental health recovery involves fixing something you can't see, it takes a lot more effort on the part of the person suffering the illness. This gets really muddied when it comes to therapists because rather than just fixing you up, they have to teach you tools to help you work on yourself. Things get even muddier too because some tools are very effective for some, while others aren't, and a bad therapist (of which there are plenty) won't really keep this in mind.

This is why you have to find someone who is a good match for you. Almost any doctor will fix appendicitis by removing the appendix, but helping heal from trauma (or whatever else) takes a lot more guesswork, and you may need to try a while to find an approach that works for you.

On the subject of "bad" therapists, it's a lot harder to easily see that a therapist is harming people because again the results of mental health work can't be seen. Complicating the matter is the fact that in many regions talking about mental health is taboo, so it's hard to know what to spot when you do find someone that isn't helping you work on your problems the way they should. This is even more complicated because when we struggle with mental health we are often more vulnerable than usual.

Basically after all that what I guess I'm saying is that it's good to not implicitly trust therapists, but I think it's dangerous to write off all therapy. A therapist that works for you can help you develop the tools you need to live a healthy life and recover from whatever ails you.