What about passwordless, email-based login? It's easier than username/password login, it verifies the email address, and it provides the same level of security (assuming password can be reset via emailed link).
> it provides the same level of security
No, it absolutely doesn't.
If an attacker breaches a user's mailbox, and then uses a 'forgotten password' process to gain access to another system, the user will know about it - their existing long-lived session would be killed, and the password they remember/have saved will no longer work.
If the attacker simply uses the mailbox access to use & delete "login link" emails, they could make use of this to access the victims account for as long as they have access to the mailbox.