Depends on where you are. Depending on country it can range from no one giving a shit, over to getting letters from your ISP, over to getting smaller fines, up to getting railed for your life.

If a website has a German version, try using that. By law every web page here must have an (pretty much) directly findable button to cancel your account. Even when you are logged out. It normally is positioned in the footer of the page. Search for “kündigen” on the page and fill in the form.

Note that not all pages still do this. But normally even just threatening to sue should add it, as they really wouldn’t be able to go against this in court. Tho crunchyroll does not seem to have this. Maybe I should create an account and do some trolling.

Or just use GDPR and write a cancellation mail. I am pretty sure in most countries they need to accept it. Do not forget to add a deadline of a few business days.