When Hall, Nash and Hogan returned to WWE in 2002, it was attempted as the original NWO back and white.  It obviously didn’t work, but was that more on creative and how it was booked, or was the whole NWO concept just dead anyways and was just a bad idea even
on paper before it was created for their return?

The whole concept was dead and buried before WCW even came to an end.  In fact the whole idea of a billionaire bringing in anti-corporate rebels was itself ludicrous.