They recently sent me an email saying something like "we noticed that you're not reading our email, so we're unsubscribing you." Apparently I hadn't been loading their tracking pixel/script/CSS, so they thought I wasn't "engaging" enough. This was despite the fact that I clicked on links to full articles, which had all sorts of tracking info embedded in a redirect.
A responsible email publisher offers a clearly-visible "unsubscribe" link at the bottom of the email, which will unsubscribe you with a single click. No nags, no checklists of email categories, maybe an "are you sure?" page at most, with equal-sized "yes" and "no" buttons. One or two clicks, and I don't hear from you again.
A dodgy email provider is more likely to "use lack of opens to reduce volume." If I don't trust some company to actually unsubscribe me when I ask, I'll just filter their domain directly to the trash. Clicking on spammers' "unsubscribe" links is usually a bad idea.