The genome of every living thing contains a record of every change that has ever happened to the species since life first formed on this planet. That is why more than 95% of every genome is just junk. The only exception is for deletions which are discarded. Sequencing the junk permits a kind of mapping that sequencing of functional genes does not permit because the junk is not constrained to function by natural selection and so can mutate without effect. This serves to provide a molecular clock that can be calibrated against the fossil record and radioisotope dating to confirm dates of separation for related (all life on the planet is related phylogenetically) species. Intelligent Design hypotheses are strangely silent on the question of this genetic detritus of the evolutionary history of the species.
You are ignoring the fact that sharing of genetic material among all species is possible through the agency of viral transduction. Bacteria share genes through plasmid transfer between species. Again, you are ignoring the fact that the experiment of life is conducted on such an extraordinarily massive scale that there is more than enough opportunity for the opportunistic origination of novel useful sequences by entirely random processes.
If that was true then it would conclusively refute and scientifically disprove natural selection (as responsible for the narrow issue of creation of life, at least) because natural processes are prone to losing data after enough natural events have passed, and only intelligent design has been shown to be able to retain all data for any reasonable length of time.
For instance, a rock doesn't retain the data for its precise original shape for its existence prior to being eroded by natural processes, nor do acids prior to interacting with bases.