Yes. Having centralized ownership (to whatever extent) is a concern for sure, but it’s a hypothetical concern in and of itself: “what if the leadership does bad things?” Is different from “the leadership is currently doing bad things.”
Decentralization helps. But if the networks effects aren’t behind it, jumping from platform to platform when things DO get bad is also viable.
Yep. Not even always ads exactly, but just dummy notifications to make your dumb brain keep opening the app or website (which is kind of a self ad).
Most apps I have to disable or heavily tone down notifications in some way to get them to stop yapping about nothing. Even then, sometimes you can’t get notifications you do want without junk.