It’s a risk reward question then. That would 100% slowdown the initial federation if it needed to pull in every community and even if that was accepted, should every instance constantly poll any instance it knows about for new communities? Also you aren’t guaranteed to need all those instances anyway and then that’s just a waste of space and processing power. Correct, it limits interactions but only to what’s necessary which allows instances to be ran on lower powered hardware, allowing more people to join in. With the possibility of third party tools I don’t see much of an upside of building that into lemmy.