Typically the efficacy stamp does come with whatever caveats came up during FDA approval - for example, my SSRIs came with two sheets of double sided paper listing in excruciating detail the potential side effects, and reminding me on every page that the pills may just make me want to kill myself so watch out for that.

SSRIs being top of the list of drugs that "sometimes work sometimes don't" I think are a good example of why the FDA rubber stamping efficacy are still good. I'm not convinced I'd had those sheets of paper if drug makers had the run of the market.

I've never actually seen evidence that a "free market" (i.e. drug market with no FDA) results in a better world for consumers, unilaterally.