I don't think that because creativity is a guideline for creating a work worthy of protection implies that the act of creativity is required in order to be responsible for copying. This not only doesn't follow its a complete non sequitur. It is unrelated to any law or precedent or even a common sense reading of the law.

The person who actuates the creation of a copy including by just pressing copy on a copier is guilty of copyright infringement. If the party that produces the recipe to create a derivative work is guilty they are guilty because they acted to enable that actual act of infringement or not at all not by some magical transference of responsibility based on a creativity test that you literally made up from whole cloth. If combining 2 works you paid for in a way not foreseen by the authors on your own computer is within the boundaries of copyright, which it is, then then the challenging to prove tangential responsibility for enabling infringement poofs like the morning dew under the bright summer sun.

In your magical transference of responsibility theory the mod creator would have had to prove that creating a derivative work out of someone else's work was legally acceptable a hard task.

In reality it is incredibly obvious whom is making a copy and any perceived ambiguity is merely you failing to understand copyright. Its also reasonable to suppose that copying the files you paid for access to to a different folder is either a) no different recording a program to view at a different time or b) no different than the copy that is created in ram to run the software. The first is fair use the latter is explicitly protected by law.

https://www.law.cornell.edu/uscode/text/17/117

(a)Making of Additional Copy or Adaptation by Owner of Copy.—Notwithstanding the provisions of section 106, it is not an infringement for the owner of a copy of a computer program to make or authorize the making of another copy or adaptation of that computer program provided:
(1) that such a new copy or adaptation is created as an essential step in the utilization of the computer program in conjunction with a machine and that it is used in no other manner,...

Nowhere is it stated that this ought to be limited to using the sofware in a manner approved of by the author. Such restrictions would have to fall on the EULA and we would have to suppose that it was acceptable to toss on additional restrictions AFTER money had already changed hands and with no recourse for the user other than to eat the loss of money AND value.

Basically its not just that your argument is flawed. It is creatively flawed in multiple ways which would be harmful to user freedom. Personally I don't look forward to your world where shovels come with contracts of adhesion that describe what kind of tasks they can be used for consulting a lawyer before I dig a hole more than n inches deep and paying an addition fee per day where I used it beyond approved use cases.

I have no idea why ideas which would be wildly stupid applied to real things somehow sound tenable to some people when applied to software.

Selling software should afford you no greater control than selling shovels and the people that want to argue otherwise need to push off.