When people are vulnerable to something that doesn't mean they should have to go through it. There are many examples where it will make a human weaker in the end. There are also many examples where it will make a human stronger, but I think in his story it made him weaker because he lost 10 years that he otherwise presumably wouldn't have.
Not only did he lost 10 years, he lost 10 relatively foundational years (i.e. it's less bad to "lose 10 years" in your 60s to 70s compared to your 20s to 30s due to the compound interest effect that early "good years" have).
When I look back at those years I used psychedelics my only real takeaway from use is that the mind is an interesting machine and drugs make me dance funny. Maybe it's because I don't know a spiritual crowd but even my old buddies from rural working class places just found them entertaining, I never heard a single story about spiritual breakthroughs.
For folks who have little real spiritual understanding (most Americans), this can seem very enticing