They are scared to re-code. Scared that it'll mess up the whole game. Just like how Minecraft was planning to release a more realistic graphic but they canceled it. Too much recoding and it might mess with other shlt.
They can't handle Android's model-less core, and they can barely manage to handle Shaman's skin tone. I highly doubt they could handle changing the graphics at all.
RF first launches the game on lowest settings by default. Theres been a guide to enhancing the graphics thru your video card settings since OGP. http://forums.playredfox.com/index.php?threads/how-to-get-nsfw-graphics-if-you-are-nvidia.1634/ As for "new mechanics" the game does that thru scrolls i.e. Volador/Luchador/RedStorm introducing ground re-bound combos, Flare having a burn/bleed mechanic, or Spike having a kG that is essentially a combo modifying stance. Thats how RFs more often than not always introduced new mechanics.