No, legalizing safe illegal highs would save lives. People are using these dangerous, untested chemicals because they can get them without running afoul of the law. People don't smoke spice because they prefer it over cannabis, they smoke it because they can buy it at a headshop.
This. Cannabis and MDMA are thoroughly tested, MDMA especially since it was intended for clinical use. They are about as well undersood as any psychoactive substance. It is batshit insane to insist that rather than legalise them, it's better to test a whole other class of substance that are just trying to replicate the same effect.