The data isn't entirely useless. It might be a good signal of areas to point legitimate research toward
Narrowing down areas into "Anecdotally many people say it works, we should check" does have some value, even if it does just wind up debunking the claims
In theory, maybe. In practice, there are far better sources of signal for far more valuable therapeutics to develop.
There are far more promising development targets than there is development resources. Self-reports from a bunch of the most drug-addled people in the world are not going to make it to the next-most-viable target.
Narrowing down areas into "Anecdotally many people say it works, we should check" does have some value, even if it does just wind up debunking the claims