Truth of the matter is that even the simplest species in the evolutionary tree are still around. There is absolutely no reason why the evolutionists are not able to show common descent from existing species. The only reason they cannot do that is because there is no common descent. The three simplest forms of living organisms - the archaea, the prokaryotic bacteria and the eukaryotic bacteria did not descend from one another and there are no intermediate species to show how such a thing might have happened. There are likewise no intermediate species between the major families and orders of nature.
(tallhappy voice:)
You do not know what you are talking about. (Sorry!)
A population speciates. That creates a new fork in the tree of life. When it happens, this is not a big deal, just a speciation.
Later on, each of the paths from the fork has created new sub-forks of its own. The fork itself has become a genus-level split. Later yet, we might say the fork is at the family level, because the descendant populations are that different now.
You're saying that you can prove the fork never happened, using the lack of living intermediates between the things at the tips of the branches on fork A and fork B. But there was never a middle fork, so the middle fork has no descendants. The commonalities the creatures at the branch tips have are with some lost ancestor.