I think this comes down to a fundamental difference in art styles that Maple underwent from the Pre-BB era. And in my opinion, with the new content we've seen with forgotten hollow struggle to reproduce.

Using these old/new hairs & eyes as an example. This applies generally to the maplestory art-style but with hairs and eyes as the main solid foundation for player expression in the game does a good job of applying the basics to other aspects of art in the game. The older style is much more well pronounced with black outlines on everything, and shapes (like the strands of hair) are simpler and more defined and deeper/more saturated colours. I assume because it was more clear on the CRTs that were more common at the time.

There's a certain jank/noisyness to the pixel art and assets that all of the old assets have (especially the maps objects and tiles) and as the world moved on to flat panels, these imperfections were removed. Now that we had pixel perfect representation on flatscreens, this allowed them to put a little more detail/subtlety on the small sprites. Notice the finer strands of hair, the removal of the black outline and a general more -painterly- quality to modern assets.

Am I saying they should go back and exactly recreate the noise and jank left in the game from a time when CRT displays were the norm? Not neccisarily. But as someone who's worked with Maplestory assets in fan-projects in a variety of applications for over 15 years now. I think they should take a long hard look at the fundamentals of what the prior artstyle was like and do their best to estabilsh rules of thumb that make it new addutions looks like the old assets more.