Unsubscribing is the polite option, but this obviously isn’t what you signed up for. I wouldn’t unsubscribe, just mark as spam. If enough people do and they start having deliverability issues of important emails, maybe they’ll change their ways… but probably they won’t.
edit: They’re probably not sophisticated enough to have separate lists, so you may have unsubscribed from everything, at least if you mark as spam you can find their important emails in your junk folder.