Clippy was annoying for the same reasons a lot of software today is annoying. It was one of the O.G. poster children of the industry's "flipping the narrative" around computing: In the good old days, the user commanded the computer, and the computer obeyed, and then waited for the next command. Instead of the user being the sole operator, Clippy "suggested" and "recommended" and intruded into your computing. It inserted itself into your work in a way that computers hadn't really done before. This is why it was deeply hated.

No longer was computing a stream of commands from the user, telling the computer what to do: Now the computer itself had an opinion about what you should be doing on your computer. And the opinions kept getting stronger and stronger throughout the years. This was the beginning of the long, horrible march towards what we have today: Notifications, alerts, suggestions, "discovery," pop-ups, "did you mean...," forced upgrades, hundreds of processes running in the background that you never ran (but the computer manufacturer or OS vendor decided on their own to run). Now our computers are mostly just running what other people tell them to run, and occasionally loop the user in or offer them a token choice. The user is more of a passenger than the driver now.

This is Clippy's legacy: A computer you barely own, running software you barely have a choice in running, force-feeding you what the computer manufacturers, OS vendors, and 3rd party apps want you to be fed.