macOS as an operating system has been "completed" for about 7 years. From that point, almost all additions to it have been either focused on interoperation with the iPhone (good), or porting of entire iPhone features directly to Mac (usually very bad).
Another point of view is that macOS is great, but all ideas that make it great come from 20 years ago, and have died at the company since then. If Apple were to build a desktop OS today, there's no way they would make it the best Unix-like system of all time.