just because email is often the defacto identity on the internet doesn't make it a good idea (bandwagon fallacy). i don't consider email tokens to be a serious form of authentication. unless you send the user their authentication secret with data encrypted by the user's public key, i strongly recommend against any use of email-based authentication.
* there are a huge number of middlemen in emailing that you have to trust. the sending email provider, the receiving email provider, ISP, email client, the device the client resides on. and everyone else in between.
* unless you're just hosting an email server on your local network, starting up an email server that can successfully get its messages across the internet to your intended recipient is an extremely high barrier.
email is an extremely error-prone protocol. there's lots of reasons that government/health organizations don't send you personal private information by email and instead send you an email that says to come log into their secure platform to view the private information.