> Google staff have no incentive either. Solving this won’t help with their promotions.

I don't think people appreciate that this is really the key observation here. In large institutions, for anything significant to happen, there have to be incentives and alternatives, and these are set by management. Management in turn usually cares about their incentives, and the company overall mostly cares about the bottom line and the financial reports.

As a result, this is unlikely to get addressed, unless there is significant pressure, like media coverage, people mass-resigning from Gmail, or major email servers blocking Google. But none of these are likely to happen.