Activation, introduced in Windows XP, is the main reason why I consider Windows 2000 the high water mark of Windows. The Windows NT lineup was truly no nonsense, no fuss. Unfortunately the merger of consumer-focused Windows (which used to be the 3.1/95/98/Me) lineup) and pro-focused Windows (which was the NT lineup plus Windows 2000) coincided with the introduction of many annoyances, starting with activation in Windows XP and later adding nagging prompts for updates and security-related things, telemetry, UI changes, and more.

Sadly even macOS has gotten more annoying over the years with its various nagging prompts.