Knowing AWS SES rules and seeing the lack of context from your post, I'm going to guess that either you're embellishing the story, or your content quality is low enough that users see it as spam. 50 a year that is one a week; I need to be super motivated to stay subscribed to a 1-a-week email from a single content provider.
Bounces also have their own system and should be handled by your email system as well.
Could be bounces, but mostly just users who literally signed up clearly for my email list with 0 deception marking spam.
It's actually cut my content production down because I'm afraid to email. From 50 articles per year to 12 to 4 to 2.