It's not really a ground juggle, in the sense that the opponent is never considered grounded. When they hit the ground, they're in a brief slide-state, which is its own state. If a character were just laying on the ground, it either wouldn't hit them or wouldn't put them into full combo like it did in that video.
Also, many moves that launch do exactly what you say, it's called air control. Some moves don't allow air control and lead to guarenteed combos, but moves that do allow you to control the direction you travel in when launched into the air, making it so that things will only combo if you air control in the wrong direction.
I'd have to disagree on combo-breakers, though. They work fine and good in some games (Hell, Mortal Kombat 9 would be downright stupid without combo breakers) but Calibur does pretty fine without them, as Calibur really doesn't have combos that go above 40-45%, and even those are usually both: A. rare B. only do that much damage on counter-hit