> But that data is reasonably only accessible by the people who instrumented that tracking
No way — the network itself is always listening: https://en.wikipedia.org/wiki/Five_Eyes
I bet it's possible to map every single human's social connections given enough time to correlate their network activity, e.g. a message-send on your phone that causes a notification to be delivered to your friend's phone. No need to break TLS or do anything other than encourage people to make as many network connections as possible all the time, record the fact that a given IP address has sent or received data, and wait days/weeks/years for enough correlations to filter out from the unbelievable volume of noise.
TLS-all-the-things actually makes this problem worse because now every single connection has to leave my network to hit some “““trusted””” origin/Cloudflare/whatever server instead of just being cached at my gateway.