I've had some experience with lsd and mushrooms, and find them to be interesting and fun to do sometimes, but not too often or too much. Having experienced a bad trip, it's really not fun and anyone who tries them should definitely do their research and only partake in safe situations with safe people.
I am probably an outlier on this topic in that I believe that all drugs should be legalized or decriminalized. If it were up to me, it would be possible to purchase any drug in a known dose and purity from a legitimate producer who is inspected and taxed, with revenues going to treatment, research and information campaigns to make the inevitable use of mind-altering substances safer.
Whether they are a net positive or not is a difficult question. For me, it was, because my experiences allowed me to explore thoughts that I otherwise may not have had, and shifted my perspective in a positive way. I don't think that every person needs to try them, or that young and inexperienced people should do them without considering the risks. There is definitely potential for therapeutic use in controlled settings, and that could be a huge net positive, if it is carried out safely and research shows that it helps.