So, back 15 years ago or so, most people who wanted to discuss topics on the internet, and who didn't want that discussion to be ephemeral, found forums dedicated to those topics.

There were thousands of forums. Millions of them. Some had dozens of users, while others had 10s of thousands. Many of them discussed similar topics.

Browning Lemmy or kbin is like browsing thousands and thousands of subforums across dozens of websites. Some of those websites have similar subforums, but they might be populated by very different people having very different customs and discussions.

Reddit kind of pushed everyone into a single room, and in a single room only the loudest people get heard. Hundreds of thousands or millions of subscribers just leaves most people shouting into the void, having no meaningful conversations, and rewarding performative antagonism and biting sarcasm.

You know, toxic shit.

The best thing to do with multiple communities here is find one that you like best, and engage with it. If there's something actually interesting going on in one of the other ones, trust someone to cross-post it. Some of these communities may not take root and grow, but some will, and they'll each take on their own flavour, and serve their members, not the machine.