It's really great that people are thinking/writing/talking about this. I think one of the biggest issues with the Web Monetization API is that the compensation metric (time on page) is far too crude. I also think needing to get preemptive buy-in from both content consumers and producers is a big reason why it and similar solutions like Flattr haven't taken off.
With the upcoming Readup subscriptions we're going to be offering consumers not only a better compensation experience (choose your own price and read anywhere on the web, Readup takes care of sorting out the writer identification and subscription distribution based on your reading automatically) but also additional premium features (better, distraction-free reading experience, reader-only comments section, follow your favorite readers and writers, etc.). It's an even simpler proposition for the content producers: We reach out to them to send them the money they've been earning on Readup and help them increase their engagement on the platform!