This registration quirk is the nature of whole fediverse: since all instances are connected open registration attracts bots and spammers giving them the access to all other instances -- creating the work for admins in every other instance. So, all major instances closed their registration to combat spam.
After signing up, admin approves the application (typically it takes about an hour) and then you should verify the email address
Anyways, I do understand that many things are quite unintuitive for beginners which is typical situation for major part of open source projects. That's a nowadays reality, it's true
Same situation happened with twitter and mastodon: twitter users were puzzled by instances, approval forms, toots, federation etc etc. Bit by bit situation improves on both user end and UI of the product itself
