But definitely isn't worse than alcohol and fentanyl and 6MAM are both used medically. The damage from krokodil, as you mention, is from the impurities. Not to mention, krokodil wouldn't even be a thing if people had access to the usual schedule 1 substances
One of the reasons those drugs are expensive is because of the illegality. In states with permissive cannabis laws the prices have fallen enormously. Not to mention people could easily grow poppies if it were legal to do so and extract the latex