This is not outside of the realm of possible. Google does nothing to stop spammers, makes up their own non-public rules and doesn't communicate with the Internet community, so Gmail addresses are already on shaky grounds.

For instance, for starters, go search through all of your email for any email sent from Google servers where the "Reply to:" doesn't match the "Mail from:", and tell me if there are any legitimate instances. We could all benefit by starting to reject all Google sourced email with a different "Reply to:".

What we really need is a blocklist / allowlist system which tracks the millions of Gmail email addresses. Has it never been seen before? Reject it with a message telling them to go sign up for the allowlist. Has it been around for a while? Allow it.

Google can't be asked to keep their own spam in check. We have to force it on them.