I think we already do. When you buy a bottle of decongestant with phenylephrine, you're just buying a bottle of placebo, and this is the most commonly purchased type of decongestant.
For those unaware, phenylephrine should never have passed FDA trials. It was whisked through almost certainly at the behest of Johnson and Johnson to provide a replacement for the very effective psuedoephedrine, which happened to be a relatively easy methamphetamine precursor.
Then, for J&J to have the gall to market phenylephrine as "Sudafed" was just the cherry on top. I wasn't aware of all that at the time, but the first pill out of a box of new Sudafed was so ineffective compared to the previous pill from the old stuff that I had to look it up.
I found this to be a good read/overview:
https://www.science.org/content/blog-post/uselessness-phenyl...