They've made / completely focused on the repos that you own and work on (and added some Copilot stuff I can't see because I don't use it), instead of the social media-like "Feed", which is now on a separate /feed page.

Opting out just makes the Feed appear on / again. I'd rather they just give you the option instead of doing the opt-out-until-we-remove-the-opt-out thing, the coward's way to change a default.