They're right here on the threadiverse
Yeah, nowhere near the size of reddit, but who wants that? Easier to have discussions without bazillions of people posting crap like "works for me" or being dicks.
I don't really trust other alternatives. Being unfederated, they rely on a closed source solution maintained by a single person or very small group of people. There's nothing in place if the plugs ever get pulled, everything is lost and like reddit, whose to say these owners won't turn their website slowly into the cesspit reddit is?
Yeah, an instance owner of lemmy/kbin could theoretically pull the plug on their instance or enshitify it, but you can just switch to a different instance and keep accessing the content you were.