Unfortunately, Tim Cook does not have the force of personality to stop it. Nobody does. Only Steve Jobs could do it, and that is likely exclusively down to the fact (whether you consider it as such or not is beside the point) that he saved Apple. The fact is, if you tell the shareholders no too frequently, you stop being in charge. And even if the next guy shares your vision, will his replacement? How many CEOs does it take until you get someone who will pursue short-term profit at any long-term cost?

CEOs have force, be it personality or investiture by the board.

No, if Cook fails to "stop" ads that's pretty clearly evidence he's okay with them.

Tim caused ads, so Tim doesn't need the force of personality to stop ads.

Tim wants ads. Tim is a money guy, not a product guy.

And if everyone is doing it to scrape more profit, then there are few options to turn to protest with your consumption habits.

People keep on talking as if Tim Cook is against this but has to follow along. The CEO of (by many metrics) the biggest company in the world can in fact stop things he does not like for the most part.

The simplest explanation is that Tim is fine by it. He has agency as much as everyone involved here. And honestly people act as if Jobs wouldn't do the same shit in some variation or another, as if these people all aren't trying to balance a billion things to make money. Nothing is sacred.