Mental illness is really difficult and complicated, and I don't think there's a strategy that works well for everyone. My experience was the opposite of yours: I experienced horrible depression for years on end, and therapy always seemed to make me feel better for the afternoon, but when the feeling faded after a couple hours, I was no better than I had been. I concluded that it was a nice relief, but it wasn't resolving the problem.
To my mind, resolving a mental health issue is a bit like resolving a technical issue like a slow-loading web page. Similar looking problems can be caused by a lot of different things in the toolchain. Just in my case alone, I have identified causes in the spiritual, physical, psychological, and lifestyle domains. As in, I know certain things cause the problem because I can trigger it via those methods, and ameliorate it by avoiding certain things or embracing certain strategies!
I think if you have a problem with a cause that is well-addressed by therapy, it will work very well for you. That doesn't invalidate that other people have other problems in other areas addressed by other strategies.
If you hang out around people talking about mental health issues, you will hear some really weird stories. Like, I'll tell you one about me: the final lingering symptom of the depression was suicidal ideation. It was more or less of a problem for me for about ten years -- more or less once a week I'd wake up thinking, "I hate my life, I want to die". You know what finally put it to bed, dead and gone, really truly doesn't bother me anymore? Tactical firearms training. I kid you not.
Buuuuuuuuut it's not really a path I'd recommend to anyone else. ;)
Medicating mental health issues -- either under professional supervision or not -- is a huge hot button issue for some people. It can be a lifesaver and it can be a life destroyer and people have really strong experiences with it and strong opinions about it. I think the whole discussion is emotionally magnified precisely because insanity is so horrible and people need there to be solutions that work. Desperation and trauma are an environment that breed superstition and excessive faith, and make thoughtful inquiry and understanding difficult. That's not evil - it's just human. Nasty problems are hard to think about clearly.
It sure is a funny space, though, because there seem to be so many solutions that work for some people. Some people are able to solve seemingly intractable mental health problems with diet - Jordan Peterson is a famous case, for example, of someone who approached a terrible anxiety problem with a very exotic diet and found it effective. You can find a lot of less famous cases of that. And the recreational drug side of it has some remarkable stories, too. Some that seem miraculous and amazing, and some that seem like people haven't really gotten a handle on what's going on.
I'd say "let people try stuff", but I don't even think that's the right approach. As you say, a substance may be a crutch for a specific person, which doesn't rule out the possibility that it's a cure for another, but which on the other hand doesn't rule out the possibility that someone who thinks it's a cure for them is wrong. I think it's good to tell each other about the pitfalls we know of and to try to improve our understanding. Sometimes people think they've gotten things right, and they're really wrong. Then again, sometimes extraordinary things are right. And on the third hand, perhaps you're one of those weird cases that really won't respond unless you eliminate broccoli from your diet or have a priest pray for you or go on a guided meditation with the right guide or become a decent marksman with pistols. Perhaps you need something weird and you haven't found it yet, and maybe you never will, and a crutch that lets you live your life in the mean time is very important.
I guess all I'm trying to say is this whole thing is a big, complicated, messy problem. I certainly have my own fears and bad experiences in the domain, and I do try to let people know about the dangers I wish I'd known of. In fact, I mostly agree with you - long term medication of mental health issues is very scary for me, and I'd have a hard time not wanting to check up on someone who was doing it and make sure they were sure sure that this was a good idea, just because so often it turns out not to be. But I also think in this space, you have to give people a lot of room to do what works for them. Sometimes it's really weird stuff.