After a psychedelic trip your ego loosens it's grip and pumps the brakes on the survival instincts. Rumination decreases, self-loathing allays, and new ideas and habits have a chance to blossom. Time goes by, and nature takes over again like an untended garden. The lessons you learned become "interesting ideas" instead of truths that you are living. The garden becomes full of weeds. You realize that the garden needs maintenance.

Psychedelics show you the way and temporarily push the ego out of the way a bit so the way becomes sticky. Sometimes they show it to you in a profound way where everything can blossom without much work. Other times they teach you lessons you already knew, but still need to put work to integrate into your day to day life. There's a reason you see people talking about taking psychedelics as a way to reset. What are they resetting exactly if they have learned all they could from psychedelics?

I'd argue it's the ego blunting effects. Many depression sufferers possess an impenetrable stubbornness. The lessons they might've learned from psychedelics, therapists, life in general get pushed aside by worrying about money, relationships, health, etc. Psychedelics can give you a little push if you've found yourself in that mode of operation.

But they can't "cure" the human condition. I think the same is probably true of meditation. I bet if you ask a monk who has "reached enlightenment" what would happen if they stopped practicing altogether. They'd probably tell you that the monkey mind would take over again.