Failed because the Storage device was too slow & inflexible & expensive (MO Disc is a nice idea but really an expensive R/W semi-archival medium) and the Product too expensive and hardly any applications to take advantage of the GUI.
Display Postscript probably too slow. Open GL is a better idea.
So the innovations?
Using MO instead of floppy or HDD. Bad Idea. MO complemented Floppy and HDD.
CD ROM already existed as a cheaper RO distribution medium. It was 4 years before Nextstep adopted CDROM!
A dock on the WIMP GUI. Hardly earth shattering. The GUI wasn't an innovation.
Display Postscript: Like MO disk a nice idea but not practical. Even today still a bad idea.
NeXTSTEP was an impractical Niche product. Only Steve's Charisma kept it alive so long.
Steve was into IMAGE, not genuine SW & HW innovation. He killed the Newton (which was then innovative) rather than bother to understand the potential and fix it. The Newton needed to be fixed not killed. But it wasn't his idea and it didn't seem cool.