If people dont care enough to mess with their browser settings thenselves, then they can either a. join a privacy-focused Mastodon instance

"Joining a privacy focused instance" is exactly an opt-out approach so the answer is exactly the same is before, opt-out is the wrong chocie.

live with the fact that choices are being made for them. People need to take actions for themselves, we cant treat everyone like babies.

It's not that choices are being made for them, it's that they are adversarial choices. There's a difference between "treating everyone like babies" and being on their side. Users who want sites run by predatory jerks already know where Elon's site is. The fediverse's main appeal afaict is that it's run by people who aren't like Musk and Spez. That is, its operators can be trusted more. They should be looking out for the user. They should make choices for the user that the user would want them to make. Otherwise there is no point to it.

This article looks good: https://www.wheresyoured.at/never-forgive-them/ :

The people running the majority of internet services have used a combination of monopolies and a cartel-like commitment to growth-at-all-costs thinking to make war with the user, turning the customer into something between a lab rat and an unpaid intern, with the goal to juice as much value from the interaction as possible.

I've only started reading it though. Anyway, if the fedivese has anything to offer, it's a respite from that. Stop trying to ruin it.