>yeah, I"m going to find in favor of the would-be infringer here because Nintendo didn't go after that C64 port that one time in 2019."
That’s not how Law works. Your mixing confusion in the market place and laches...the jury doesn’t pick and decide what laws apply.
If I saw a T-shirt with Mario on it for example, or a Mario game...I would surely think the owners of the Mario marked either created or licensed the work...that’s the definition of confusion anyway, but that’s not the issue being discussed.