Juggles were already a huge part of the game in Tekken 2/3 MMaRsu. Outside the strings, they're this game's way to do combo's and to punish a player who didn't block your launcher. Hell, it even says it huge in the game. The info bar frequently tells you that learning how to juggle is an essential part to winning a match.
Personally though, most of the juggling is quite easy to do. Most characters have a couple of obvious launchers where you just add a simple string of moves after it while your opponent still hangs in the air. That's all there is to it.
The real key is actually to avoid these launchers alltogether by blocking, dodging in time and making sure you learn this game's wake up game. All easy stuff to do, and all explained in the game's manual. The only trick here is to get used to the game's timing which is actually pretty mild.
Don't give up so quickly just because you're used to SC4/SF4.