The genocide of the Picts was a medieval myth . Most contemporary historians of the period point out the gradual gaelicisation of Pictland long before the accession of Kenneth who may well have been pictish himself and was described at his death as King of Picts . The Dupplin Cross close to the important royal centre of Forteviot has gaelic references to Pictish kings prior to Kenneth . Kenneth's son Causantín , complete with pictish name , was described as King of the Picts which is odd if his father had just destroyed them . Alex Woolf describes Kenneth as “the fifth last of the Pictish kings rather than the first Scottish king."
And again, why would a warlike (and apparently rather good at it) people like the Picts willingly adopt another language and renounce their group identity. What was in it for them? These are questions I'd need answered..........
The King list , like the above was written centuries after the most of the kings had died . Considering that the Picts had no written records they were unlikely to be accurate , they are false up to just before the the time of writing , that is different from being falsified which suggests some tampering of the “facts “ . The use of gaelic was part of the assimilation of that language and culture into that of the Picts ,it can be seen in material culture where the earliest Pictish stones had no christian iconography by the mid period around the time when Kenneth was crowned , Christianity the religion in the Gaeltachd , informed and was mixed with Pictish symbols , by the end of the tradition the Pictish stones had a only christian symbols ,a clear transition rather than abrupt revolutionary change .