Gmail's spam filters always err on the false positive side. It's always been like that. Add the opaque nature of google operations, and you can't in good faith

Gmail's spam filters always err on the false positive side. It's always been like that. Add the opaque nature of google operations, and you can't in good faith place the deliverability burden on third parties. It's like trying to hit bullseye in darts in pitch black darkness. Best to assume gmail is flawed, which it is, as the parent poster did. At some point Google will realize the image problem and act.