Yes, exactly. Control groups are incredibly important for ensuring good quality of clinical studies. It's a technique that solves multiple "calibration" problems, including:

- being able to draw causal conclusions

- being able to adjust against placebo effects

A lot of clever people have tried to come up with ways of doing away with control groups. But ultimately, the best we can achieve is to stop early, as soon as the trial has a clear outcome. I do perhaps think this has become more common in recent times though, so perhaps the study you were involved in was at a time when early stopping wasn't really "the done thing".

But it still beats "studies" done 100 years ago, when you might give someone a cough mixture, see that they improved (if they died, let's just ignore that), and conclude that it was the cough mixture that did it!

No, in fact it is quite common to do "open label" clinical studies in which patients know what drug they are getting and no one is given the current standard of care. This is especially common in cancer, where the standard of care is so poor, and in rare diseases, where the patient population isn't large enough to admit such a comprehensive study.

It is harder to have the same statistical confidence of efficacy and safety in such studies, but clinical researchers try to address those issues by varying e.g. dosage quantities, time in between doses, etc.

Source: place I work is currently doing studies of this nature, and in general such studies seem to be well-understood and accepted by the FDA.

For such a large effect it is quite possible to implement an adaptive trial design with unbalanced arms and interim analysis for efficacy. But you have to ask for this, the FDA will not necessarily suggest it directly.