Now you're making a different claim. You said that manufacturing fentanyl requires all sorts of specialized equipment and knowledge. It simply does not.
Does that mean cartels aren't sophisticated manufacturers? No, of course they are.
Second straw-man: no one said homemade firearms literally don't exist. The claim is that they are a rounding error.
The startup costs, process knowledge requirements, and logistic issues with inputs are clearly higher for large scale chemical manufacturing than mechanical. The Roi is currently lower, if that changed they would adapt easily.