> because most of the population is spectacularly underpaid
Underpaid compared to what? I'll start assuming here, so please forgive me: it sounds like you mean "we have a right to not be underpaid" which would be nice but I don't think there's anyone that can bend economic realities to make this right meaningful.
It would be like "we have a right to eat meat" in prehistoric times which is simply a concept but it's not feasible simply because we call it a right. If we have a fixed amount of meat, someone will have to eat less if someone else eats more.
Yes, we can increase meat production but then someone else will again eat less than the others ("underpaid" in terms of meat).
> This makes it cheaper - so far - to use human labour than machine labour.
Yes, new technology is equivalent to putting a maximum salary on human work, eventually it's just not efficient anymore to use humans.
> It's about making all human activity obsolete
I think what you're describing is paradise and I don't see it happening anytime soon. And if it happens, well, no work all play sounds like Star Trek and there we still needed humans to work in politics, defense and research...
> All forms of culture
I think the artist that works in spite of his low income is a counter-example. There are people that like to be "productive", e.g. by making music, ...
> without much of an idea of what's actually incoming
I don't see it incoming anytime soon. But if it happens, I think must people will kill themselves by overdosing on endorphines (using drugs, social media, opioids, whatever else comes along)