NotLD entered the public domain because of a failure to apply a copyright indication. Largely due to this oversight, and entire genre of Zombie media has flourished unencumbered by restrictive IP.
Obviously your cynical take on fan-art is despicable and ignorant, but there's no shortage of examples of what the commons can produce.
Look at game companies stopping fan made games. I remember hearing about a fan remake of PS1 Metal Gear Solid. Was gathering huge fan far and had kojima's blessing, but the studio shut it down.
https://gameranx.com/features/id/159002/article/10-incredibl...
A success story for one fan project though was Sonic Mania https://en.wikipedia.org/wiki/Sonic_Mania
I have also seen theories for movies on r/writingprompts that blow actual sequels out of the water.
But then again, this is nothing new: (nsfw) https://en.wikipedia.org/wiki/Erotic_art#/media/File:Shuvalo...