Have you seen http://signup.hive.io/ ?

You can sign up via ecency or threespeak just using an email.

I made one using ecency recently, had to fill out username I wanted + email.

They send me an email confirmation link, I click it.

A few minutes later they send me the password.

I think that's the simplest account sign up process I have seen yet, and it emailed me the password so I have a backup of it. If using protonmail which is encrypted one now has an encrypted backup of their password(though you should change your passwords after getting it created so that you are the only one with the keys).