My understanding (I used to say the same thing) is that this is now understood to be false, and that placebos don’t affect objective indicators, only self reported perception, and that perception reverts to the mean over time with the placebo.
many medical complaints have no objective measure, like "how much" pain or "enough sleep". And if a sleep aid or painkiller has a reliable immediate palliative effect, in addition to its longer term effect, that's part of "the cure".