Suicide is an individual act born from personal pain within a system that still continues unchanged. Extinction is the end of a species, not of an individual. Universal extinction, as an abstract hypothetical, is about preventing future beings from having to experience suffering in the first place. One is a reaction to suffering after the fact. The other is a stance against it. They are not the same in scale, intent, or outcome. One ends a single experience. The other questions whether we should keep generating the bad experiences that can lead to things like suicide.