There is a set of ideas, which copyright law was intended to legally — ergo enforceably — embody. The set of legally enforced rules still listed under that name has changed over time, and in many ways no longer reflects the original intentions (this is largely a problem with corporate regulatory capture).
Nonetheless, it is still a feature of the laws called "copyright" that it is intended to cover implementations, not ideas. If you invent a mousetrap, they cannot sell it; but they can develop and market their own, notionally better, mousetrap.
It simply is not factually accurate to say that cloning an out-of-print TTRPG via a functional equivalent of the mechanics described with your own, original text is "a loophole." It is the fundamental principle of implementation, not idea.
I see fellow opponents of "AI" screaming on the reg that Copyright Per Se Delenda Est, and apparently none of 'em can generalise the "all safety laws are written in blood" thing to ask themselves "what could have motivated laws that foundationally declare it illegal for other people to simply take your original creations and make money only for themselves by selling them?" and I think it's a historical moment which behooves us to be fucking clear about what copyright both is and was supposed to be for, because I do not accept that we have to cede it wholesale to what they paid for it to become. I do not accept that to save the village, it is necessary for the Glorious Revolution to burn it, shoot everyone, and salt the earth while bleating "Look what corporations did!"
