Why does Peja Stojakovic suck so badly now?

I always thought when you were a great shooter you could sustain that even with age. Although Peja is obviously a great exception lol. I remember in 2004 he was 4th in MVP voting, and made 2nd team All- NBA and couldn't miss. It was rare when he missed. Now he can't make a shot if his life depended on it. Or that's what it seems like at least. What happened?