The point you're missing is that telling people "just eat less" doesn't work, because it's extremely difficult for many people to "just eat less".

That's literally the whole reason that ozempic etc are popular, because they make it easier for most people to just eat less, in the same kind of way that caffeine makes it subjectively easier for someone who's tired to be productive.

That is a simplistic description which is superficially true. The body, however, is quite a bit more complicated than that. Especially when you get to that wrinkly pink lump in your skull.