Every single reader app not every subscriber and not everyone hosts their own reader.

That's why I chose to do manual polling/clicking for the built-in reader I have for HeyHomepage.com Just a list of all subscribed feeds that one can click through. My reasoning was that since a subscriber actively and knowingly subscribed to something interesting, they might gonna click it again when they're interested again. No need to automatically poll everything all the time.

Maybe for a future newsletter/magazine function I need to do some automatic polling in the background.

> i don’t think rss comes close to scaling. every single subscriber will poll every single thing every 30 minutes (or whatever).

Well-behaved RSS clients send a conditional request and in most cases receive an HTTP 304 Not Modified response.

> this was a crushing amount of traffic 20 years ago when the web was much, much smaller…

It was?