The last release of NeXTSTEP was in the 90s. It’s fascinating how many of the concepts that are still the same, or similar. DNS, TCP/IP, NFS, FTP, resolv.conf, tar, ICMP... Some of them are outdated, but still. The Unix paradigm has held up well IMO.
NeXTSTEP was hardly related to UNIX, as in culture.
Sure it had POSIX and was partially built on top of BSD, but that was just to get a foothold on the UNIX workstation market.
NeXTSTEP was all about Objective-C frameworks, including at the device driver levels, and the same culture is at play at Apple and NeXTSTEP derived OSes.
Being an UNIX is just a story to sell and get people into the platform, nothing else, specially valuable when one is either a startup getting into the nascent workstation market, or a business close to get insolvent.