They were preaching the same about obesity for years, which achieved absolutely nothing, and then GLP-1s came along. Turns out that yes, there is indeed a hormone which can reliably be increased to cause weight loss.
https://www.mayoclinic.org/diseases-conditions/type-2-diabet...
They don't "cause" weight loss at all -- it's mostly an side effect. (sorry to be so pedantic).
Given that, the rational of the original comment makes less sense. A hormone that changed your behavior such that the resulting behavior changes made you happier is far more of an obfuscated ask of modern pharmacology, as there is no behavior change that will reliably fix the problem the same way there is for weight loss (eat less).
Isn't the effect that it reliably makes you eat less... which many other drugs do such as amphetamines, nicotine etc.
And of course, one for mental health.
The three put together would make a very interesting society.
Add nootropics to the mix and it gets even more interesting.
I would not call these "safe", so I think you might have meant something else?