Your question becomes: how many genes in 2% of the genome, and how many evolutionary steps would it take to transition that many genes? How many discrete species in between? (And that 2% figure is currently the object of great skepticism, so it could be much higher.)
What are the genes involved (those genes that would undergo mutational change resulting in evolution of phenotype)?
These questions represent only the beginning of a vast number of questions, none of which seem to be considered seriously by evolutionists.
To answer your last question, these things are necessarily elaborate because species-specific changes in phenotype correspond with vast differences in genotype.
Even the highest figure of the entire genome (a much larger set of data, as only about 3% of the genome is genetic DNA) is 10% if you “score” deletions and insertions differently; I gave the figure as 6%.
Why would there have to be so many different species to explain such a trifling difference in DNA?
The observed rate of change within the species more than explains the observed difference, if there is indeed six million years separating the two (TWO distinct populations, not thousands) species.