That is really a separate, unrelated issue.

Not everyone needs the deepest, most intelligent therapist in order to improve their situation. A lot of therapy turns out to be about what you say yourself, not what a therapist says to you. It's the very act of engaging thoughtfully on your own problems that helps, not some magic that the therapist brings. So, if you could maintain a conversation with a tree, it would in many cases, be therapeutically helpful. The thing the LLM is doing, is facilitating your introspection more helpfully than a typical inanimate object. This has been borne out by studies of people who have engaged in therapy sessions with an LLM interlocutor, and reported positive results.

That said, an LLM wouldn't be appropriate in every situation, or for every affliction. At least not with the current state of the art.