You might be surprised. The core of the MacOS is nextstep (thus the reason that modern MacOS system functions begin with the prefix "ns") and even the software development tools will feel familiar to modern XCode users.
There is a lot of elegant refinement in modern MacOS, but the bones of it are solidly NeXT.
Based on, yes, but since OSX 10.0 it's been diverging from what was the 1990s era NeXT. The core OSX team up to v10.5 or so was basically the same people who wrote the NeXT OS, and were acqui-hired.
Apple bought NeXT pretty much for their IP and software. By the time they were acquired NeXT had been out of the hardware manufacturing business for many years.
