You'd be right if ISPs didn't do mass DPI and modification of pages to inject their own ads and trackers. They also routinely hijack and intercept DNS responses. They absolutely cannot be trusted carrying unencrypted traffic.

It’s a problem because regardless of whether it needs to be or not, it is.

The point is that https-everywhere people have successfully pushed the majority of the sites that could previously be served over vanilla http to require https anyway. Now if you're on and old device you need an https proxy or else you're out of luck.

a) yes it does

b) it is literally trivial to buy a tiny RISC chip for a dew cents that can handle HTTPS just fine