X makes a platform available. People choose to post on it knowing full well how it works. X makes money by running ads, charging for subscriptions and tracking users.
To me it sounds reasonable that you can't just take that content and repost it without their or the author of the post explicit permission. It sounds like a fair use case and copying the whole content is not that.
Now there are technical details: "are they really copying or generating on the fly for the user" but I don't think it matters. At the end of the day the content belongs to either X or their users. I think arguments against that are arguments against copyright in general.
If I ever posted something on X my expectations would be that if people want to read it they need to obey X's terms and conditions. I wouldn't be happy if there was a platform copying it somewhere else. If I wanted my post to be public I would post on freely available public website (and then maybe repost or link it from my X's account).
To me it sounds reasonable that you can't just take that content and repost it without their or the author of the post explicit permission. It sounds like a fair use case and copying the whole content is not that.
Now there are technical details: "are they really copying or generating on the fly for the user" but I don't think it matters. At the end of the day the content belongs to either X or their users. I think arguments against that are arguments against copyright in general.
If I ever posted something on X my expectations would be that if people want to read it they need to obey X's terms and conditions. I wouldn't be happy if there was a platform copying it somewhere else. If I wanted my post to be public I would post on freely available public website (and then maybe repost or link it from my X's account).