The spore drive still works with the information initially imputed into it from the Tardigrade, as I understand it. It needs a living component to engage the drive because of that information because.. uh.. DiscoveryI always got the impression that it was basically one in a trillion chance they stumbled on that tartigrade, without which the spore drive didn't work and that whatever Samets did to himself couldn't be replicated. Of course they kinda blew a hole in this with Book's species being able to operate the spore drive, so yeah, not sure why others weren't able to develop the technology.