Apple tried to create a new OS and failed (during Jobs's absence from Apple), bought NeXT, then used NeXT's work as the basis for the very successful OS X. And despite this, in your mind NeXT is a failure?
TBH I'm surprised you're arguing. NeXT is generally accepted as a commercial failure. Hell the NeXT cube, alone, was a famously collosal flop. This isn't even a little bit controversial.
Jobs cared more about changing the world and advancing civilization than he cared about providing good value for investors. NeXT was a very solid success when measured by the yardstick of what Jobs set out to do.
Trying to make money by creating a new general-purpose operating system is inherently a very risky enterprise. NeXT's investors knew that.