Login error: "Please update your scanner"

I decided to boot up Ingress on my new phone today and to my shock, I wasn't able to login. It gave me an error saying I have to update my game and redirects me to a playstore page for Ingress Prime.

Why is this? I just wanted to use the original Ingress app, now renamed to "Scanner Redacted", that I have been using since 2013.

After trying to reproduce it on another account, I finally found the reason.

It turns out that when I changed my login email, it marked my account as a new player. New players who started after the release of Ingress Prime are unable to use Scanner Redacted.

As such, players who change their login name will be locked out of the old app indefinitely.