(Think Big, Regarding your first point, I’m not sure. I do hear your point. But I suspect it depends on a case-by-case basis, and there is no hard and fast rule. If it is given appropriately [i.e. privately] it may be fine. Sometimes tochacha requires public embarrassment, if the person remains obstinate after getting private tochacha. In a tznius case, that may cause may harm than good i.e. other members of the public may inappropriately be called to attention of the problem, causing them to sin. So that surely may be an issue. But even the initial tochacha is questionable for the reasons you mention. But again, if done quietly perhaps it is proper. I would pose such a question to a halachic authority, since it does raise questions as you suggest.
But absolutely, the root causes must be addressed more so than the symptoms. But sometimes when the symptoms are flagrantly displayed, it is necessary to first address the symptom, and then the root.)