I think you're both overthinking things. There are more drugs, that are more powerful, and they are more easily available than ever before. Fentanyl is easy to make (thank you biochemical advances), easy to distribute (thank you massive e-commerce market for the camouflage), easy to buy (thank you crypto), and a rice grain's worth will kill. This isn't because of DEA policy, or a slippery slope, this is human progress meeting human flaw.