I get your complaint in general, but it does not seem like this is a good example of throwing random unrelated stuff in.
If I want to do writing I'll use one of the 6 tools on my PC more suited to that task.
It's _also_ useful in my apps dedicated to writing and even the text areas of browsers. I think it's all about implementation though, Apple's writing tools are quietly buried in the context menu for most text inputs. Microsoft has a tendency to be pushy and in your face about their latest AI offerings like shoving it into the Start Menu, or making it a prominent and visible element of their UI (Copilot in VSCode, even when you're not a subscriber) and the Verge's screenshot isn't enough for me to judge this by.
WordPad would be a much better place to shove in a complex feature like AI.
In these cases, the best tool is the one you've already got.
I use notepad to write quick notes or to strip formating from text.
(and i hate with a passion when a program tries to be "smart" - hello clippy)
I don't believe it's useful. I don't think Notepad is a "writing app." And I'm fairly certain not a single user in the history of ever has asked for this.