The problem is most likely people that are new to the fediverse/lemmy just not understanding it and choosing a “default”, popular instance. I was going to pick it as a safe option when I first came here but it was under load and wasn’t accepting new users, where I then had to find another instance and settled on feddit.uk.

It would be good if lemmy instances could have the option of “load balancing” new users, so if the current instance has way more active users than it’s federated wtih then it disables registration but recommends other, smaller instances to the user.