If the Celts are even more autochthonous to Atlantic Europe than previously believed, it makes the attempt at population replacement in the remaining Celtic countries even worse than it is when it’s been believed the Celts were early invaders.
One of the tidbits in the Cunliffe lecture is that the most widely spoken tongue in Ireland is English (not surprising); second most is Polish; third mos is Chinese (!). Gaelic is still spoken (and sung) in Ireland, but not as much as it was even 30 years ago.