@taylorlorenz Use simple examples:
What if an instance admin dislikes you?
-> Fediverse: Get banned from one instance; change instance; reconnect to your friends.
-> X: Get banned from X; be lost.
What if the owner of a server wants to spread their world view or influence elections?
-> Instagram: Algorithm changed; Propaganda gets boosted; noone sees other opinions
-> Mastodon: People curate their timelines and decide what they see