I'm surprised so many level 50's are complaining they need to complete the main story. You need it to unlock content like dungeons. Also it's like.... the main part of the game, a FINAL FANTASY game.
To the level 50's complaining about newbies: I'm pretty sure people will be enjoying the brand new game and content (to them, as new players) that was created from 1-50 than worrying about Ishguard which they can't do anything in anyway due to their low level. As well, the level 50 quests post-Preatorium give EXP for 50+.