And yet many people consider modern sardinian as the closest language to old roman latin.Personally I think there would be a stronger case for Sardinians, the so called Barbagia was never completely romanised; the resistance of some Ligurian tribes to Roman rule doesn't seem to have had long term consequences that one could still trace centuries later and it probably pales in comparison to the Osco-Umbrian and Samnite open rebellion in the Social War.
And ligurians are still gallo-italic and have more in common with the lombard language and less with the others.