Her ground game is totally based on her ability to read her opponent. If that makes it bad, then it's bad. I would not say that's entirely correct, though. Her tilts are really good (especially down tilt) and her up smash and down smash are useful but situational. The problem with her ground game is more that it's built to pop the opponent upward after a read, not to do battle on the ground long-term.
If I had to say something to sum up her ground game it would be something like, "she has an answer and option for everything, but only one." Utilt is one of the best out of shield options in the game, but it's her only one, so that makes it predictable. Down tilt is an awesome ground-based move, but it's built for one very obvious purpose and isn't something you spam. Jab is a great escape move, but is easily punishable unless you do it when your opponent is in a bad position already. It's a decent ground game. Her only "bad" ground moves are fsmash and grab. Her grab is bad, but not unusable. I land grabs all the time, believe it or not, even on Wario players!
EDIT: Also, there's the fact that her ground game isn't really even all that useful because her aerials and short hop are pretty good. She plays a lot like Peach sans floating, I guess. Random video link:
http://www.youtube.com/watch?v=9k3uJd2XK8M (first one popped up on YouTube); how much of the ground game is even used here?
Well, is ZSS as good of a grabber as D3? You're allowed to tell me otherwise, I'd actually LIKE to be proven wrong with information instead of flamed or given a smarty remark..
Obviously she is not as good a grabber as King Dedede. Most characters aren't. But, it is definitely possible to grab Wario. What comes up must come down.