Nope, the placebo effect can have physical effects and be genuinely curative. The level to which this is the case is highly variable from patient to patient, but it is inaccurate to say that is limited to improving sensation and perception of illness. Not to mention, in many cases the malady being treated is one of perception, for example, in pain management. And alleviating pain in itself has downstream positive effects on disease progression and patient QOL.
Actual chronic pain sufferer here. If I had a dollar every time placebo and positive thinking was prescribed to me, I would have enough to maybe hire a doctor who won't systemically downplay or dismiss my pain because of my age and gender.
My random conjure if anyone cares:
I see it like many 'real' medicines that alleviate symptoms. Sometimes the symptoms are the ones causing the issues, EX. a fever to kill germs can kill braincells. But like any medicine that alleviates symptoms, it can also hide problems. So I see it as a case by case thing.