Here's something Apple could do: pop up a dialog saying something to the effect of, "this carrier wants to manage your wifi settings. Agree? [yes] [no]". If the user doesn't agree, that's communicated back to the carrier who is free to not render the service. Presto, Apple doesn't have to take the carrier's word that I agreed to a third party managing my networks.

That it's been like this forever doesn't make it right.

ETA: the ad-supported ISP analogy misses the crucial distinction that the ISP knows I signed up for them to MITM my data. Apple knows nothing of the sort.