A ban on marketing prescription-only drugs directly to the public existed in the US until recent decades. The amount spent on marketing skyrocketed when that ban was removed.
Since there's no way to reinstate the marketing ban short of a Constitutional amendment (basically impossible) that point is moot.
An outright ban would be very difficult now that the genie is out of the bottle. The FDA can regulate what goes in the ads, like requiring disclosure of the expected benefit, how prevalent some of those side effect them mention are, how common the condition it's meant for actually is, and of the list price of the medication. Many of these drugs are for rare conditions and the drugs, though approved, help a smaller percentage of patients than the ads portray and to a lesser extent.
But in general the traditional drug development approach of finding small molecule drugs to treat specific diseases is running out of steam. Most of the low-hanging fruit has already been picked.