In practice, no, it's more nuanced than that. Any mailing list operated through any remotely legitimate ESP will require subscriptions to be confirmed/acknowledged up front before any delivery is attempted to a recipient. If the confirmation step fails, i.e. the "check your email and click a link to verify you really signed up" email bounces, or nobody ever clicks the link, the list owner isn't generally going to be penalized for that.

If you want revenge for modal popups, your best bet is to create a bunch of throwaway email accounts, subscribe to the mailing list from them, and start reporting the individual messages as spam when they arrive. Flag them as junk at the mailbox provider (Gmail, Outlook, etc.) and use the links in the List-Unsubscribe headers to flag them at the ESP's end, too.

If you're trying to get the web site's mail server blacklisted, definitely.