IAAL but this is not legal advice; seek licensed counsel in your jurisdiction.

Copyright gives you a bundle of rights over your expressive works, but when you give them to someone else for republication, as you are here, you’re licensing them. By licensing according to the terms of service, which is a binding contract, you are relinquishing those rights. As long as there is a term in the terms of service that allows the publisher to convey your expression to a third party, you don’t get any say into what happens next. You gave your consent by submitting your content, and there’s no backsies. (Subject to GDPR and other applicable laws, of course.)

And these days, no web service that accepts user generated content and has a competent lawyer is going to forget to have that sort of term in their ToS.