Why can't Doctor's fix abnormality surrounded by people's DNA to get rid of genetic diseases?

Why can't Doctor's fix abnormality surrounded by people's DNA to get rid of genetic diseases?
You have 10 to 100 Trillion cell in your body. Every cell have the same genetic code. How would you translation that code in so abundant cells?
Additionally, the genome is turning out to be much more complicated than be thought just a few years ago. Much of a gene's 'performance' is determined by 'epigenetic' regulation of the gene's expression. You can hold 'normal' genes, but if they are not being expressed properly, explicitly the same as have defective genes.
This is a very, vastly complex issue.
because DNA is so complicated, the doctors wouldn't find a matching piece to the out of the ordinary piece or organism the human body won't accept the tentative one .
DNA is a very immensely small structure in human body. It is lacs within no and if any extra dose happens after the patient may carry someother genetic disease.
Because a DNA molecule is approximately 4 billion pairs long. To find the defective gene would take decades upon decades. We basically recently map the human genome. I think we did it smaller number than ten years ago. We have agreed about DNA for almost fifty years and it took us almost forty to map it. Without the use of supercomputers, we would hold never done it in 1000 years.
because it is not jammy to fix anyone's DNA. Can you imagine every single cell within human being containing DNA human being repaired? It's not so easy, if impossible.