That is your opinion, but the judge disagreed with you. The decision may have been overturned on appeal, but as it stands, in that courtroom, the training was fair use.

I can memorize a song and it will be fair use too, but it won't be anymore once I start performing it publicly. Training itself is quite obviously fair use, what matters is what happens next.

This is also, unfortunately, the only way this can be settled. Making LLM output legally a derivative work would murder the AI golden rush and nobody wants that