My humble opinion on Nexon's path.

Ironically, this also has rendered LaTale way more secure in terms of hacking and gold buyers get caught and banned very easily there. Literally the opposite of Maple Story in both control responsiveness and security.

The problem isn't that it shows the player doing something right away, it's that the server believes the client. If it was transmitting "I am at 0,0 and hit jump while moving left, to catch a rope at 400,0" then the server should be checking that a jump from that spot can land on the rope.

The movement skills have made it harder for Maple to autoban on this; there's a reason hackers are all Evans. They can legitimately move to anywhere in the map at any time so the server has no way to tell good blink from bad blink. It could definitely be done, but they haven't yet, and thus hackers are all Evans using bots that hack blink to teleport them right where they want to go.

The problem with verifying everything the players do is that it makes running a server more expensive. The upside is fewer hackers. So how Nexon handles it is they only add checks once the hacks exist, instead of designing it from the start to protect itself.

for one anecdote, back in the day (like beta) there was no limit on weapon speed. A hacker could just edit their weapon to attack instantly, and spam hundreds of times a minute. The solution was to introduce a speed cap (at faster 2), and have the server disconnect anyone who attacked more frequently than that allowed. Sure, they could have been tracking how fast a player was attacking from the start, but they waited til it was a problem. After that, it was still possible to edit your weapon speed, but only up to faster 2 - any higher and you'd quickly disconnect. A more thorough check would be to keep track of what the player was equipping and what speed buffs they had, and then compare packet timings to those. But the extra effort isn't worth much because hackers don't bother speeding up their weapons anymore.