I can just speak from my personal experience; it's my opinion in the early days of Poser that Zygote, then Daz had the best quality stuff.  This is not to say that there were some content creators who did an excellent job--but I will say that I'd had a lot of trouble with 3rd party stuff not having the right poser library structure, or paths, or misnamed files.

At any rate, it all boils down to if a person feels that Daz's prices are too high, don't buy Daz content.  If you don't want to invest in Genesis content just walk away.  I really don't know what the argument is.  Like the stuff use it, buy it, enjoy it.  Think it costs too much or that it should be Poser compatible, don't buy it.  I tried to resist Genesis at first, but then I tried it and I like it--but I still llike Poser too.

There isn't any right or wrong answer; everyone just do your own thing and be contented.