The reason for the strict limits on pseudoephedrine is because of its use in the manufacture of (prohibited) methamphetamine, so that's a poor example. Prescription drugs are also a bad example because fentanyl (and most other opioids) are already available with a prescription in most of the world.

Alcohol and nicotine are the only real middle ground in the US (maybe cannabis, but that's in a paradoxical legal status right now). Neither really seems to be in a "solved" state. Though I concede that at least alcohol and nicotine seem to be in a better state than fentanyl.