The reason why I quit was because it became a point to where I had to start grinding I believe, and then I couldn't get to the part because the paths were blocked by a huge stone.
Basically, it became boring.
I never grind, I just help friends / solo harder dungeons for fun and end up getting experience by doing that :D
And I'm guessing by the seal stones that weren't broken, you quit very early on in the game. Every stone in broken now, except for the ones that lead to unreleased areas. And there's PLENTY of places to go now

The part on the way right is Uladh, everything that was out before the G4-6 update.
Everything else came out on the G4-6 update. And more will be updating in later G's - The area in the middle, and a part to the way north.