I agree with you that certain types of self-help books/advice can be unhelpful and promise you the world. I fell down that hole too, but not, it seems, as far as you did. I quickly realised that I didn't have the energy to put that kind of work in. It made me feel bad for a short while. So, yeah, that kind of self-help is toxic.
However, there are others that are excellent. For instance, books on mindfulness really helped me with my depression and anxiety. Not all self-help is bad.