modern websites are a cancer that we really quite could do without

The proof is in the pudding. You claim nobody wants these things yet there are billions of people using these kinds of sites.

Just because a lot of software sucks doesn't mean it's acceptable or we should lie down and give up. We should work on improving OS capability/permissions models so that apps can't do this by default.

In the absence of better protections, I absolutely audit which processes make connections from my machine and uninstall those that make unwanted connections that can't easily be uninstalled (with a small number of unfortunate exceptions where the need to use certain software outweighs the desire to maintain a reasonable system).

This doesn't mean no connections ever, it means no conections users don't ask for and no connections that don't provide value to the user. It certainly means no phoning home or stats/crash data connection without explicit opt-in.