Couldn't you write a script to manually go through the pages and click the 'unsubscribe' button? It might be less time/effort on the author's part then attempting to negotiate with a multi-national conglomerate who will take minimum 1 quarter to ship a 'Unsubscribe All' button.

There's a long tail in many products where non-happy-path flows are undoubtedly terrible. But if product teams prioritized addressing that long tail, what would happen to the delayed mainstream features? How would the userbase, in aggregate, feel about such a prioritization? It's disappointing when they say to expect no reply, but it seems like both a practical and efficient outcome. They're an autonomous organization and you can't step in and say "put this at the top of the backlog".