i get all kinds of new communities by just clicking into the remote community, and then clicking subscribe
Maybe you misunderstand what I mean. Right now, if I were to create a new community on lemmy.world called /c/thatonekirbymainisawesome, it wouldn't show up if I searched for it here on the kbin.social magazines page. That's because kbin.social currently doesn't know that this community exists and thus isn't fetching anything from it. The same goes for any other two instances. If you want a non-hypothetical example, go to sh.itjust.works and search "geometrydash". You won't find /m/geometrydash (or at least I didn't at the time of making this comment). If you go to https://sh.itjust.works/c/geometrydash@kbin.social, you just get an error, because sh.itjust.works doesn't know about geometrydash@kbin.social yet.
To fix this, someone needs to essentially tell an instance, "Hey, this community over here exists, and you should start fetching stuff from it." On Kbin, this is done by putting the community's address in the general search bar. So if I were to search "thatonekirbymainisawesome@lemmy.world" on kbin.social's, that community would finally appear, and I'd be able to subscribe from it and see any posts made after that point.
What I'm suggesting is that instead of having to type the full community address in the normal search bar (which can be unintuitive), there should be a dedicated interface for adding remote communities (i.e., letting your instance know that communities on other instances exist). PieFed does this with its "Add Remote" interface, and I think it'd be nice for Kbin (and Lemmy as well) to have something similar.