There are many contexts where doing an experiment with proper controls is literally a crime against humanity.

Which means, yes, that there are many studies where the control isn't quite proper. And that does slow down progress in medical science.

Good luck ever doing a clinical trial with this approach. Think about cancer treatment. If we have an intervention we know is better than the natural course of the cancer, then we ought to compare the experimental treatment with the default treatment instead of letting people die from cancer in the name of "science".