It needs a lot more people and lines connecting to the centralize services, like 6+. You have 14 dudes in the fediverse, you should have a similar number of dudes in the traditional centralized social media things. You need to make it clear that every connection between two people goes through that central server. With only 3 or 4 it looks like it's some kind of small community there, like you're just saying "communities exist on Facebook" rather than "on Facebook everybody connects to one central Facebook service". It would also be good to draw a black line around the edge of the bubble to indicate it's a walled garden rather than an open system.

For the Fediverse example, it would be good to have a slightly darker shaded bubble with people around their local fediverse instance. That would indicate that there are local communities, but that they can still communicate with all the other communities. And, maybe show that people can be part of different communities, show one person connected both to a mastodon instance and a Lemmy instance.

Edit: I just thought of something else to make it clearer. On the centralized networks you could also make a darker group of people who are a community on say Facebook, but show that that community has to connect to each-other through the central server.