By 2001 the Classic MacOS wasn't really "different", it was largely the same as the System 7 release from 10 years ago.

The NeXTSTEP on the other hand was quite different. Different from MacOS, from DOS/Windows and from proprietary UNIXes. I would argue that switching to NeXTSTEP was more aligned with the original spirit of "think different" than getting stuck in the old ways.

Like another post says, "The Mac was a philosophy". I bought a series of them but stopped around the year 2000 because they threw away the philosophy in favor of innovation. I think things were going south already around 1998. Remember Sherlock? On system 8.5 it would regularly interrupt the user (sending games from full screen to windowed) to display a dialog to say that it was indexing files. This couldn't be turned off except by disabling the Sherlock extension altogether.

That says that Sherlock's mission wasn't to help the user do user activities, but to get the user out of the way of Sherlock's activities, while keeping the user informed about the magnificence of Sherlock. This attitude became really popular with every OS that was competing to be innovative, and we're still stuck with it today. Shut up user, pay attention, look at my features!