Jerome Bruner helped create cognitive science and there's a fascinating reason why he didn't care for the metaphor of the mind as a computer.
Unless I'm completely misunderstanding you, it sounds like you're misunderstanding Freud. Freud didn't say that the past completely determines the present. He presented the idea that if you're completely in the thrall of the past, you're suffering from an illness. He was a doctor; he believed this illness is treatable, that it is possible to free oneself from the tyranny of the past. For Freud, the fact that, as you point out, each new experience of memory is an active re-creation of the past, is exactly why some people can get trapped in it; they keep re-creating past traumas again and again for themselves. His idea was that through analysis, you can become conscious of doing this, and then you'll be able to stop doing it.
On the other hand, what you're writing here is the perfect description of the current brand of psychiatry, which believes that emotional problems can be solved with drugs, and what you are writing certainly explains why this drug therapy model is a total failure.