Yeah, as has been said it's not really you, it's generally how game AI is programmed. In fighters, because it's just you and your opponent with a fairly strict set of system/engine defined rules that you're both supposed to be following, it's just more pronounced.
Fighting game AI can't really think, it can only perform certain programmed patterns and react to your inputs. The problem there is that where a human will note patterns in your playstyle and, if the player is really good, occasionally react to the visual cues of certain moves they can;t just read your controller inputs and react accordingly. For a quick example, if you throw a fireball a human opponent that wants to counter it will either have had to predict you are going to throw that fireball or they'll have to see your character start to do it. An AI, on the other hand, "knows" that you're doing a fireball the millisecond you complete the input and will be punishing it before your character even does it.
Basically, fighting the AI in a fighter can be fun at times but it's nothing like fighting a human. More importantly, putting too much stock in learning how to beat the AI can actually make your play worse by creating tendencies that don't work against a human (or that might work once but never again, since game AI can't really learn in the way a human can).
Anywho, I feel your pain when it comes to Juri. I tend to play more mindgame oriented, poke and set up heavy characters in pretty much every fighting game (Hwoarang/Ling in Tekken, Lion in VF, Juri/Guile in SF4, etc.) so while I can often find ways to beat the AI there's really no way to learn how to play the characters properly that way.
