Um....medical professional here. 
Actually, you'll find that given the class of cannabinoids consists of literally hundreds of varieties, the statement "cannabis use is associated with increased risk of schizophrenia" is a blanket statement that isn't accepted as gospel truth by everyone these days.  Furthermore, would you categorically be able to say how well the study/studies you cite control for confounders such as social circumstances and adjunct drug use? Afterall it is also well recognized that mental illness has a strong eipgenetic component.
2. "Canabis makes you lazy" is another totally unqualified statement. People develop anhedonia because of the combination of circumstance and personality. Many of the "users" I know are highly functioning professionals.
3. Opiods come with myriad side effects like nausea, dizziness and gut busting constipation that don't make them appealing for everyone. 
Maybe you should speak to a few terminal patients who tried both.