Right. Figuring out the dose would not take years if it actually worked.
There are always leads, always more possibilities to try, so it's a critical scientific skill to understand how promising they actually are. Nobody will ever publish a peer-reviewed scientific paper saying "this shit is completely fucking hopeless" -- even if it is -- so you have to make that inference from a growing pile of negative evidence "we haven't been able to replicate / determine dosing / find support for" and from the shift of attention to different theories.
There are always leads, always more possibilities to try, so it's a critical scientific skill to understand how promising they actually are. Nobody will ever publish a peer-reviewed scientific paper saying "this shit is completely fucking hopeless" -- even if it is -- so you have to make that inference from a growing pile of negative evidence "we haven't been able to replicate / determine dosing / find support for" and from the shift of attention to different theories.