First, as others have pointed out, Star Wars does not reflect RL space combat and physic. It doesn't even try. What it tries to do is convey the feeling of WW2 areal combat in a space opera. Thus the TIe fighter. It is cool, iconic and utterly spits in the eye of practical fighter design. Turning and peripheral vision are not concepts that were considered with the TIE.
Second, and again this has been said, it is not about what ships could barrel roll If you hated your troops you could barrel roll your CR90. What you couldn't do is barrel roll a CR90 effectively while in combat. If fact, if you add "effectively in combat" to the end of each maneuver, it makes them make more sense. otherwise flight would look closer to the Babylon 5 Starfuries.
