I interpret your last line as "If an E2E test fails because of a product bug, the result should be a unit test". I've been fighting this fight for a decade now

I interpret your last line as "If an E2E test fails because of a product bug, the result should be a unit test". I've been fighting this fight for a decade now, and I'm pretty sure I've never won it for a whole team. The best I got was that people would pre-populate bug fix code reviews with reasons why they couldn't sensibly unit test this particular issue. If you have had better success, please tell me your secrets!