Cannabis is the introvert's dream drug. I was pretty introverted from 17-20, until an acid trip kind of permanently changed my personality and social confidence.
During those years, cannabis was my ambrosia. I am already very introspective when I'm sober, so cannabis and psychedelics just send the introspective introversion in to overdrive, it is just amazing. My first and most intense (3 hit) LSD trip at 21 was experienced alone when my parents were out of town, and it was astounding. I don't think I've ever thought so much in my life, I broke down the mechanism of time and was able to truly define it in a tangible manner.
Opioids are nice for the lonely introvert, filling that social hole in your personality that is missing, but they don't provide any substance, nothing real, just a state of artificial contentedness. Being content does not equal being happy, which can be truly be achieved through the power of our minds. Cannabis and LSD are just a jetpack for our minds, so we can provide happiness ourselves. Opioids take all the fun out of it, they just do the work for you in a half assed way.