Portal and Portal 2 are now on the switch, not sure how age-appropriate those would be for an 8 year old tho

Let me see if I underatand this correctly:

If I create an account on a random, small instance. And then go to the "all communities" feed. I can automatically see all communities that are in my instance. In addition to that, I can see all communities of other Lemmy instances, that are "federated". But I cannot see other communities from other nstances, unless I go on there, find the communitis and manually subscribe to them (I believe there are other ways to get them to show up, like using the search etc.?)

So, as a normal user. Who's just looking for a replacement for /r/all, wouldn't joining the largest lemmy instance that is fedarated to many others (Just by how many users it has, because it's the users who link instances by their actions?) make perfect sense?