MS has WordPad... fck around with that to make it support markdown or whatever else beyond rtf you want it to support. For that matter, it's probably that much more appropriate to do so.
Do I typically use Notepad, no.. not really... I actually use the new rust based edit terminal app more than Notepad. That said, I expect notepad to do one thing... edit text files, and to not break doing so. The ONLY* addition that might be acceptable would be a HEX Editor mode, so you can edit any file.
There are maybe 5-7 applications in Windows I expect to never break... task manager, notepad, registry editor, file explorer, command prompt are at the top of that list... these are the golden tools that should never fail, even if everything else does.