Regardless of this entire PE debate, we would still have a problem, on the web, of data being out of reach due to walled apps that only serve rubbish HTML.
The problem of open + semantic data is very relevant to this discussion but we're pretending that one "side" has all the answers. I want a better web -- more open -- more semantic -- and maybe some shimmer of a truly semantic web[1] will emerge in the next 20 years.
So, yes, a 100% JS App is 100% awesome if, IMHO, it has:
* A publicly documented and consumable REST API
* Semantically enriched data through that API
* Some kind of degraded state NOT just for search-engines but for older devices and restrictive access (e.g. behind national/corporate firewalls)
I am not interested in being one side or another regarding this PE feud, and I am sure you're not either. I am trying to question what is best for the web and humanity as a whole. I don't think we have a silver-bullet answer. I do think it's necessary to dichotomize walled web-apps and open websites, and the latter deserve additional thought regarding usability, accessibility and semantics.