Well, I think the other team is shooting 50% because most of their shots are layups and dunks. You'd expect most players to nail layups and dunks.
I guess it all comes to defense and whether your players are getting back or not. Somebody suggested that the 'Crash Board' option should be off, that way your players can get back on D faster. That and forcing your opponent to take more outside shots as well I guess.
I mean, I don't wanna sound like a teacher or anything, but that's what I can gather from what you've explained.
Have fun playing the game mate!