It's been fascinating to watch the system software evolve over the days, from a simple small OS that only had 1-2 basic applications, to the wealth of systems/applications in today's environment. iOS, iPadOS, tvOS, watchOS... and they all have the Mac to thank. Or, more specifically, Mac OS X, OS X, and now macOS.
To think that in 1984, a simple OS with a trash can, menu bar, and mouse pointer to get people from point A to point B started whole new generations of the OS... and nowadays, what we have is a trash can, menu bar, and mouse pointer. Pretty much the same, fundamentally. It's just that from 1984 to now, the OS has grown so much, added so much complexities, and went through quite a few transitions. Motorola > PPC > Intel > ASi. Throughout all this, the core Macintosh OS has stayed the same, pretty much, at its tight core. It's still an UI-based operating system designed to get people from point A to point B, to help people get needed stuff done, to type documents, play games, connect via social media, watch streamed videos online, and so many more.
What we see now, with Big Sur, with its flashy UI, is still the Macintosh, ~25 years later. Mac OS X turned the Macintosh around, made the user experience better and more user friendly. Sure, there were some bumps down the road, some dud versions, but the OS has came a long way in stability and maturity in the last 20 years.
Happy birthday, Mac OS X, err OS X, errrr macOS. It's been a great 20 years, and I look forward to the continued evolution of the OS, and who knows, the roots of then-NEXT OS/Mac OS X may lead us to a brand new system in the future.