At risk of sounding like a grouch: Hachi was full of it and grabbed on to a convenient meta commentary about Vocaloid's decline that was practically invented for him. I also think most modern retrospectives that treat Sand Planet as a catalyst for Vocaloid's resurgence or a line dividing eras are probably overstated. All that said, it is as much about Vocaloid on Nicodou specifically as it is about Vocaloid as a scene in total, and read from that perspective Nicodou is even more of a sand planet than it was eight years ago, so maybe it does have some truth left in it.
It's worth reading some of the interviews he did around then if you haven't before.
https://vgperson.com/vocalinterview.php?view=hachicut2