Most content that gets posted on social media is 'stolen' from another social media site. That's not really an issue.
But there are bots posting up threads from subs like AITA (complete with links to Reddit) where there's no point engaging with a non-existent OP, so the threads do not get any engagement. And they often get posted in massive batches so it fucks up your feed too.
Lemmy needs to develop its own culture and that is made harder by people trying to make it a mirror of Reddit.