But when you need to edit text the only thing you can be guaranteed to have is notepad, which (a) has no features and (b) does the basics of text editing terribly

How often does that really happen though, in terms of needing it for general system usage? I have worked in Windows all day for my entire career and it hasn't come up much. When it has, notepad is almost always sufficient to deal with the edge case.

For other kinds of text editing, just download and use whatever text editor has the features you want for the task at hand. If notepad had to be all things to all people it would be bloated and not particularly good at anything anyway, so it's better that it remain a lightweight simple text editor in my opinion.

In their defense, that wasn't Notepad's original purpose in life, hence it's name.

Microsoft unsuccessfully tried to supplant Notepad and Paint but met harsh resistance because there is a disconnect between what these Apps were originally intended for and how people actually use them day to day.

Snip & Sketch comes really close to replacing Paint for 80% of my needs, but I often use Paint to quickly mockup UI, something you can't easily do in S&S yet.

There's nothing from Microsoft that even approaches replacing Notepad for me. Notepad++ is my preferred editor but even it is overkill.