If enough expected messages don’t show up, users are going to start thinking gmail is broken. The problem for Google is that they are not the only trusted brand consumers interact with. I’ve seen a lot of stuff start ending up in spam that shouldn’t be there. If enough password resets, customer service responses, and order confirmations aren’t delivered, it looks like Google has a problem. If it doesn’t even make it to the spam box it makes Google look really bad.

Google has definitely been changing things, everyone presumes it’s some rogue ML system. My company had solid Gmail delivery for almost 10 years, and at a fairly large volume. Now we can’t get it delivered any more. Very close to showing users a message not to use Gmail.