Having had been a part of the beta they weren't old to me. I spent like 3 years playing the game before you could jump down through platforms... However I still get a tinge of nostalgia for the newer classes (and I enjoyed them for a bit, before nexon decided new classes didn't need to be balanced and reworked all current classes), but I feel what I would most enjoy seeing out of the KoC content is the maps, monsters, and music, not the classes themselves (as someone said they were just new flavors of already released classes) I actually thought about this the other day, it would be so cool to release Erev, and Edelstein and so on, at level brackets they weren't originally, filling in some of the gaps in the game (or adding more new things to do at all levels). Killing those ice puffballs outside the Aran place at level 50 because the monsters are level 45, taking on the Edelstein at 150 after clearing out ToT. I don't know. I feel there's so much potential with the material, that won't mess with what is currently in game if it's done right... it also just feels so Maplestory like... I mean, Orange Mushrooms are terrifying at level 5, why do all later monsters have to be so scary? <--- I mean, imagine this thing having 160,000 HP and tanking hits better than Chief Oblivion Guardians? Reminds me of the Slime tree in 2005 on my bowman and being terrified of dying because potions were expensive and cute slimes could literally put me in a grave. The music though, excuse me as I go listen to Rain Drop Flower on repeat...
There's of course a variance in how old school maplers view the game but imo KoC are not old school. Royals is, for me and probably most other players here, what we envision and how we remembered maplestory to be. Keeping it simple is honestly probably royals' ticket to success.