Perhaps I must emphasize that my point is subtly different from the parent's: whether those people are genuine or not fundamentally is irrelevant: a miracle drug with essentially no drawbacks is a fairy tale. It's almost certainly a lie.
(That's why the parent think they could be ads, unless he's deeply cross-referencing South Park…).
The loudness of that lie ITT might also drag people down an unhealthy path: it's irresponsible not to speak up about it.
We know obesity is one of the absolute worst things you can do to yourself as a human.
We know that being prescribed diet and exercise has not helped hundreds of millions of people in the world stop being obese.
We do not catch every long term concern when developing a medicine - but we do catch a decent amount! We know specific mechanisms to be concerned for, e.g. angiogenesis and the likelihood of accelerating tumor growth, lots of others. We do not see any mechanisms that would point towards health risks anywhere near the level of obesity.
So the realm of concern lies around possible long term side effects that we're not aware of.
If you find yourself in a room that is on fire, and you see a door but you're not sure what's on the other side of it, are you going to refuse to open it because there might be something worse on the other side?
"Too good to be true" is also just an aphorism, not a law of nature. It's certainly possible that are negative long term impacts from GLP1 medications, but should all of the people that have been unable to remove one of the single biggest health risk factors in human history via diet or exercise not pursue an option that we know is highly effective at removing that risk factor just because there might maybe be something worse years down the line? We're not talking about acne or hair loss here, man.