I don’t fully understand how lemmy works completely yet. But for example I made an account at Division by zero and subscribe here to post. Is it not just a more inconvenient version of making a reddit account and being able to post practically anywhere?
Also what’s the difference between making an account at one instant and just making one centralized account for the social media?
The advantages of the fediverse are that there is no central ownership or structure of data. Your data is just your data, and your instance is just where you decide to host it.
You can sign up on one mastodon instance and start tooting and gather a following, if your mastodon instance starts enforcing rules that you don’t agree with (such as federating/defederating with meta) then your following belongs to you, not your mastodon instance and you can migrate your account.
Similarly the different services are just ways to present the same data as delivered by ActivityPub. I can access data posted to a Lemmy instance from Mastodon. I can follow pixelfed accounts from Mastodon. I can follow Mastodon users from Kbin, etc.
Right now big social media is like writing in the guest book and they let people look at it if you fill their requirements.
Federated social media is like sending an email to a public inbox that anyone can subscribe to as long as their instance maintains good standing with the sender.