Dream it. Pitch it. Launch it.

wouldn't want nexon running my game.

They would be kinda running your game, but not really. You'll see that they're asking for the submitter's references/resume. They wouldn't ask someone this unless they were intent on hiring you ("Launch It"). Although it's not explicitly stated, it sounds like they would want to make you the project manager of your own game.

Also, I can't see how people are taking "Maplestory is dying!" out of this.

1. Nexon wants to create a new game.
Therefore: Maplestory is dying.

Just because a company wants to expand does not mean that their old products suck or are dying. It just means they want to expand.

Also, don't read into this too much - you get $1,000,000 in support of your game development. Nowhere does it say that you just flat out get $1,000,000 for an idea. You have to follow through with your swing and do the project. You'd likely collect royalties from them as long as they run your idea and that's how you make your money. They're also investing in you as a person just as much as they're investing in your idea, so a sound game development and project management resume would be likely.

Another thing to notice is that they did not guarantee a winner. They could go through this entire process and get no new games with it. Also, they did not guarantee just one winner. They could find five new projects. It's really up to them.