Like I posted upthread, one of my complaints is that a lot of the good stuff in Worlds and Monsters was not reproduced in the core books.Which section of the PHB, DMG, or MM is this Worlds and Monsters in so that a new player picking up one of these books has access to read it as part of the game?
But even the core books have quite a bit of flavour - more world background in the 4e DMG than the 3E one, for example, and more world background in the 4e MM monster entries than in the 3E ones (just some random examples - in the demon entry I get the history of the Abyss, in the spider entry I learn that Lolth was once a god of fate, in the goblin entry I learn about the religious and cultural practices of hobgoblins). And the 4e PHB gives more details on the gods than does the 3E one, and it gives us bits of world history scattered throughout the race descriptions.
Anyway, I know from my own experience that it's not true that "nobody understands it or likes it as much as something well designed" (which is what you said) - I understand it and think it is well-designed (and Worlds and Monsters explains the design) and I like it. I like it as much as Greyhawk (which I've GMed in for many years) and better than FR or Eberron, neither of which I have any interest in running a game in.