So turn those features off. I just checked, there’s a setting for both spellcheck and autocorrect.

Lots of us use notepad on hundreds of different machines, many times freshly installed. "just turn it off" is not a solution as that increases the unnecessary burden beyond the utility of the application.

A bigger sin of new Notepad is that its no longer ephemeral when not saving the file. This is really bad if you happen to copy secure data into notepad for brief evaluation or manipulation. It now gets saved unencrypted to the file system in a temporary file whether you want it or not.

Or just use wordpad instead of turning notepad into wordpad?

There’s a reason we opened notepad and it wordpad. Adding features and bloat to notepad removes that.