I'm a old player, I played it when there wasn't even third job, when it was a hell to lvl up
anyways, back then I played Maplestory for about 6 years till I had to stop.
But everytime I tried to came back to play I feel something is missing.
It's not only the nostalgia but the game lost a huge part of it sucess: the social aspect.

My suggestion is... a new server wich would nerf all the dmg, where would be truly harder to lvl and to boss alone
to bring the purpose again on having party to train to lvl faster, to even low lvl bosses you would need to do party
To bring purpose again on do party quests, to revive the soial aspect off the game wich made it so popular
Not like reboot nerf, but a server where you could also use cash shop (gacha) but just somehow nerf the dmg so hard that people would have to play together again.

Why nerf?
People don't have to do parties anymore to train, they dont have to do party quest (wich was fun)
because everything is so dam easy,....You can zakum easily alone on lvl 12x
While back then you had to do party. So you would get to know people. It was fun cuz I made friends and for everything you had to depend on other people.
Now you just lvl up easily to 120 and everytime alone. Lvling in MS lost all sense of achievement...I guess nexon made easier to lvl so people can try all jobs and stay more time engaged on MS, but you didn't need it back then, cuz lvling was an accomplishment and people just want to get stronger to defeat bosses with friends (or to be the top something of server)

Marketplace is also a lost place...People would reunite in marketplace and It was fun browsing the stores to search for stuffs

I bet many old players quit cuz the game became to easy and souless
And some new players quit easily for the same reason...it's not addicting playing alone.

* my english is not my first language.