A Christian believing Biblical story and Chronology and an Evolutionist whether Christian or not will have diverse opinions about what was too complex for people enumerated in genealogies before Noah or even whether they existed or not.
But not even evolutionists need suppose that Genesis comes from an age when man had no mental capacity for understanding a concept like "millions of years". Biblical Hebrew and its Greek translation does have expressions meaning millions. Like in Daniel ch. 7 verse 10:
A swift stream of fire issued forth from before him: thousands of thousands ministered to him, and ten thousand times a hundred thousand stood before him: the judgment sat, and the books were opened.
Ten thousand times a hundred thousand = 1000.000.000
Vedas and Mahabharata and Upanishads are pretty old literature too. Unlike Hebrew literature not in having the concept but in applying it to years. I am not sure which one of them - maybe more than just one - states this thing about Himalayas very slowly wearing down until the world is destroyed and recreated, but that too is very clearly pre-modern writing and shows pre-modern civilisations contained men capable of grasping the concept in question.
Silmarillion, though never meant to be factually believed, also states age of earth as very old, far far older than Genesis says. And the statements have nothing like modern scientist or rationalist sound, but clearly expresses the concept in a clearly pre-modern way. Which is enough of an answer to a statement like in the title.
In a Christian Evolutionist the statement is only erroneous. He may believe Genesis simplifies the view point of the Omniscient God to adapt to people who could not grasp a concept like "millions". This is not good theology, as it makes God a kind of wellmeaning liar. But at least it is comprehensible how they reason.
An Evolutionist who was an Atheist could not say such a thing. He would have to argue Hebrews shortened genealogies before they began writing or took them up again after a long break and then their mistake was sacralised by coming to be included in a sacred book. A position which is of course not at all acceptable to a Christian.
Since in last two essays I have stated I know about but do not believe Silmarillion, I do foresee one standard question from some atheist readers. How do I know the Gospels, let alone Genesis is not fiction like Silmarillion and Lord of the Rings? The short answer is: peoples (Hebrews and Christians) have accepted them as their earliest records. None has made such a mistake about Silmarillion. A more detailed answer is not given on this blog, since it is dedicated to the special debate between Genesis and Darwin believers, with author on the Genesis side, but on another of my blogs:
Enjoy the reading!