In an ideal world I think most mental illness could be treated in a similar way to how the rich used to treat it back in the 19th century (probably still do) - basically go off to some resort in the countryside, have your basic needs like food and washing taken care of, have immediate access to social groups and spend some time every day working on your problems with someone. Spend the rest of the day swimming or drawing or playing music or whatever. Just give people some breathing space to work things out. Obviously this is not feasible for the majority under capitalism.
Personally I’m pretty cynical towards therapy’s ability to help people who are suffering from their environment. Of course there are mental illnesses that are unconnected to this, but I think they are the exception really. I actually see a psycho-therapist (not specifically Freudian but works along those kind of lines), and if nothing else, at least it’s more interesting than my experience with more conventional therapy, and certainly no less useful.
I don’t think the worry that Marxists sometimes have about therapy - that it tries to make people content with an unjust and fucked up world - is particularly valid. Even if the root of our problems is capitalism, the point of therapy should be to adapt oneself to the world as it is, and that doesn’t mean you can’t be discontent. I do think there is a problem, with psychiatric treatment in particular - and I’m not opposed to meds, I’m on them myself - but it can inculcate a feeling that one has to be feeling good or happy or safe all the time, which (speaking as a former addict) is the same mode of thought that people have in addiction, and can often lead to total stagnation and an inability to confront the pain of life.
“ anything that can't produce evidence of efficacy.”
This in itself is kind of a minefield. It’s very easy, for example, for pharma companies to prove that their meds can make more people feel better than random chance. It may be much harder to prove that other types of therapy, - particularly those that involve long term work - are more successful, even if they have the potential to have a much more significant impact on a persons life than just temporarily improving their mood a bit. Not disagreeing that the profession needs a purge, but unfortunately it wouldn’t be as straightforward a task to evaluate outcomes as it is in other forms of medical treatment.
Really what is needed - within the confines of capitalism - is to make therapy free and readily available so that people can find what works for them. I mean it even makes sense for capitalists to do that, in the sense that a happy worker is a good and content one. But neoliberal austerity will never allow it. To that system the working class are unthinking cattle to be herded with a club.