People hate WW?
From what I've seen, a lot of people rate it as their favorite game in the series.
It was really popular when came out despite lacking features that the original version had.
But it was a lot more popular than the original and is the introduction to the series for most people, and as it was the first game in the series with online play, it was the one that built the Animal Crossing online community.
The problem is, as an early DS game, it has aged horribly, looking almost 2D, framerate often in the single digits, it's a wonder people were so impressed at the time
When City Folk came out, it was honestly not really a sequel and more a re-make with a handful of features that people took for granted, it sort of became clear how lacking Wild World was.
It's by no means a bad game, but it is so dated that it's hard to play outside of a quick nostalgia trip.
Then New Leaf came out making City Folk seem lacking in comparison
Even if City Folk ran a lot better, I can't wait for the Wii U AC game to see the series back at 60fps again.
Tl;dr, It's not really hated, but once the rose tinted glasses come off, it's just not as fun as people remember.