So your saying, that even properly sourced and credited, using someone's artwork is always wrong?

I remember a big argument about video game companies taking down youtube "lets plays" of their games because they said that it made less people buy their game. When, as you said, video games were meant to be experienced on an individual level and that everyone's going to have their own feelings with the game. People who inevitably won the argument raised the idea of "Free publicity"

I see many of the same arguments applying to artwork. Is it not nice to have someone else who likes your artwork spreading it around? Even if they are making their own content with it? (Characters and lets plays)

That's why this is such a grey area, in my view.