There’s so much about your ancestors that DNA will not tell you.
DNA will not tell you when your ancestor was born. DNA will not tell you when your ancestor died. DNA will not tell you what your ancestor’s occupation was. DNA will not tell you the house or lot where your relative lived. There are many other things that DNA will not tell you about a specific ancestor.
And DNA tests, to be used effectively, must be used in coordination with traditional genealogical sources. That coordination may not be necessary when testing for connections within one or two generations of the testee, but more distant relationship “proof” usually requires more than a few swabs of spit to establish.
DNA is an additional tool.
It is not the only tool.
It is not a replacement tool for all other tools.