A lot of novel readers shitted on the series later on because they thought Maple is too strong for no reason, so I'm gonna put the words out for you manga readers.
The reason no one will ever be able to reach Maple's level of defense is because of this patch, specifically the monster aggro change, devs made it so that no one can sit doing nothing for hours and still have their defensive skills continously level up just like Maple did. (in a sense it's a buff for Maple)