I've heard this a lot, and personally I've had a lot of good success with a prompt that explains some of my personality traits and asking it to work through a stressful situation for me. The good thing with this rather than a therapist/coach is that it understands a lot of the subject matter and can help with the detail.

I wonder if really what we need is some sort of supervised mode, where users chat with it but a trained professional reviews the transcripts and does a weekly/monthly/urgent checkin with them. This is how (some? most?) therapists work themselves, they take their notes to another therapist and go through them.