there’s no fair use/dealings defence of them.
The OTW, who run AO3, would disagree with you: https://www.transformativeworks.org/faq/#faq-WhydoestheOTWbelievethattransformativeworksarelegal
That said, I'm not sure why they say 'transformative works are legal' rather than 'transformative works are sometimes legal and we believe noncommercial, transformative fanworks are legal but no one has actually tested it in court and it's unspecified in the legislation'.
I'm confused. Are you running out of games to play? Do you only play on console or something?