As Goat has said, this platform (Lemmy) is comprised of instances, some, like Lemmy.world, are general instances, and some have a specific theme or type of content they cater to. There's one for furry porn, one for regular porn, for example, and one for utterly insufferable Internet communists who make a point of behaving badly in other communities.
I wanna push back on this. The whole point of federation is that people from different communities interact, but when an active community like hexbear predictably has a ton of people leave a comment on a post that reaches their /all page it gets called "brigading" when it's literally just people using the most basic feature of the website.
Sorry, but no. I've seen how they engage with other instances, their strategy is to dogpile on anyone who dares disagree with them, flood the thread with insults and shitty images, and generally behave like poo flinging monkeys. They don't debate, they don't actually make a cohesive argument for their beliefs, their entire approach is to use overwhelming force to drown out opposing voices.
The Fediverse is much more than just that. You just described the Lemmy (and kbin?) part of it. The Xitter alternative Mastodon for example is another part of the Fediverse among many others.