I disagree - aside from blog sites or marketing/portfolio type sites basically every web application on the modern internet requires per-user dynamic content to

I disagree - aside from blog sites or marketing/portfolio type sites basically every web application on the modern internet requires per-user dynamic content to function - e-commerce, banking, productivity apps, social networks, messaging etc. the modern web is all about displaying and processing users data. Really any distributed cache is only going to be useful as a replacement for existing CDN's serving static assets (and thats totally fine - it would be great to see the democratization of the performance & scalability of a global CDN)