Yes, somewhat. Communities are like subreddits. So yes, if a community is doing what people don't like they can pick up and make a new community. A good example is on reddit r/gaming used to be more discussion and news focused but over time it became more popular and filled with memes. Some in the community didn't like this so they made the r/games subreddit which is news and discussion focused.

On lemmy, that new community can be made on the same instance or on a different instance.

What I was getting at, was that in addition to this, if the communities on an instance dont like how an entire instance is being run, they can pick up shop and just move to a new instance. As a user you'd have to make a new account on a new instance, but you'd be able to subscribe to all the same communities on the instances you like.

To simplify: Instances are run by admins, communities by mods. On reddit your only option is to make a new subreddit and change your mods if you don't like something, but you will always have u/spez as your admin. On lemmy, you can ditch your admins and set up shop with other admins.

To answer your kbin vs lemmy question: The only reason you would pick one over the other would mostly be due to their layout and customization. Additionally, instances can block other instances, so you might like kbins layout, but maybe they block an instance that has a community that you like. Like. Conversely, kbin might have a cool community you want to subscribe to, but your specific lemmy instance is blocking it. So you can do what I said above, you pick up shop and you set up in an instance that doesn't block the community you want to join. Alternatively, you can set up your own instance on your own server and then you can join anything you want, provided that you aren't so toxic that other communities potentially block you lol.

I have general helpful additional links in the bottom of my sidebar over on my community https://lemmy.ml/c/ps5 if you want to see how you can do some of what I said above.