Actually WoW (and most mmorpgs) is meant for both casual and hardcore gamers. Its the attitude of the hardcore gamers that causes casual gamers these feelings.

It's that feeling of being left behind while everyone around you grinds and grinds. I saw that when I played WoW. I told myself that I'm not going to grind my arse off (after grinding in the ever so demanding Lineage2) in some other mmorpg for sometime.

Speaking of RP servers... you'd still be a bit left out too if you join in late. Everyone, even though role playing will still be off to quest and raids which you can even qualify for.