You're comparing apples to oranges - those are social networks where multiple people have to come to some sort of consensus, having rules over that consensus sure, can be a feature. I don't need anyone to agree with me to turn off notifications.
It is, though, and examples have been provided of VERY successful platforms built upon this negative space.
Consider the lack of a feature as a feature itself; it lowers the amount of cognitive brainpower required to use the system, and that is VERY valuable.
Incredibly good for mental health.
> The only option I see is… options. User-specific customization.
You can SSH into a remarkable tablet and do whatever you want to it.
> How does a company make a product that sells to a sufficiently wide market to make it worthwhile?
It is very expensive. Its only purpose is to be a digital notebook.
Think of this product as very expensive paper that backs up writing to the internet. Not a sh*ty tablet that can't do a lot of things.