NeXT used 'Display Postscript' a display server that was basically a inferior copy of Sun's NeWS system. This was later changed because NeXT was to small and Adobe didn't want to support Display Postscript anymore. Sun of course killed NeWS because they wanted to be a 'standard'. Next didn't care about standards. They had less applications then CDE Unix, and far lower deployment in the 90s.
Objective C is one of many language that you could use to build UI libraries on top of some display system. Objective C wasn't the best or inherently better then many others. Objective C adoption by Next was kind of a historical accident based on office location.
Having something VM based for UI development isn't actually that much of an issue, when the hardware manufacture delivers the OS with the VM included. And usually it his the hardware manufacture that delivers the OS. And VM bases system can be integrated well with the core OS, object oriented or not. And that VM are inherently to slow is also questionable, specially for UI apps that can use C libraries and the Display Server for the most performance relevant stuff.
Apple itself had a very nice system for UI development on Dylan that was arguable better in many way then the Next system. But when Steve Jobs came and they had Next, that wasn't developed anymore.
What Jobs showed of in the late 90s wasn't exactly revolutionary stuff. But Jobs always presents everything as revolutionary.
IPhone development in 2010 working the same as Next development in 1990 is a sign of 'failure', not of success.