How were people making morphs for all the years when there was only Poser? When zbrush didn't exist or wasn't a standard?

Never said you have to have zbrush. You can use blender or magnets and the morph brush if that's what you want. And there's scripts that import morphs for you if you can't get them to import correctly on your own.

Pretending Poser is impossible for people to make content for doesn't make it true.