It's more like "They can draw what they want, and should fully understand why any problems occur."
I guarantee you fanart, and other media, of franchises that aren't as oversaturated right now don't have this problem. If you did...say, a piece to show your liking of the Shin Megami Tensei franchise, as a random example, you probably wouldn't get a single problem from it. The franchise is pretty quiet, and it's not plastered on nearly every "main" webpage of the internet, and so people wouldn't think twice about its existence. However, if you do a piece for say...FNAF, since people are getting bombarded with that daily, you'll get more backlash like "Ugh, more FNAF..." and so on.
I guarantee you fanart, and other media, of franchises that aren't as oversaturated right now don't have this problem. If you did...say, a piece to show your liking of the Shin Megami Tensei franchise, as a random example, you probably wouldn't get a single problem from it. The franchise is pretty quiet, and it's not plastered on nearly every "main" webpage of the internet, and so people wouldn't think twice about its existence. However, if you do a piece for say...FNAF, since people are getting bombarded with that daily, you'll get more backlash like "Ugh, more FNAF..." and so on.