Lemmy.world is very popular, and one of the largest instances. They do a great job with moderation. There's a lot of positives with lemmy.world
Recently, over the last month, federation issues have become more and more drastic. Some comments from lemmy.world take days, or never, synchronize with other instances.
The current incarnation of activity pub as implemented in Lemmy has rate issues with a very popular instance. So now lemmy.world is becoming a island. This is bad because it fractures the discussion, and encourages more centralization on Lemmy.world which actually weakens the ability of the federated universe to survive a single instance failing or just turning off.
For the time being, I encourage everyone to post to communities hosted on other instances so that the conversation can be consistently access by people across the entire Fediverse. I don't think it's necessary to move your user account, because your client will post to the host instance of a community when you make a comment in that community I believe.