My impression is the Iceni were a pretty sophisticated civilization. They sure gave the Romans fits.
Perhaps, but it doesn’t appear that they stood out from the other Celtic tribes. Had they not been conquered by the Roman Empire, then the Angles/Saxons/Jutes/Danes/Norwegians, then the Normans, they might have risen to a mighty nation state after they’d sorted out their internal differences. Cavanaugh asked the Normans to land in Ireland to help him fight another petty king, and began British influence and eventual dominion over all of Ireland, for example.
Boudicca went hog wild and raised her own tribe and parts of various others, carried out some massacres and town-burnings, then led her reckless overgrown gang of killers into a funnel-like abatoir; until the last ranks got to the point where they could see the unbroken (and no doubt weary) line of Roman infantry, they’d helped push the rest of the uprising right into the killing chute. Reportedly 70,000 Britons perished fighting in that last battle, and the victorious Roman commander apparently rounded up and slaughtered every Iceni tribe member who could be found (the Celts used tribal markings) and the Iceni’s allies.
If the battle site could be found, there might be a mass burial of the slain nearby, and who knows, perhaps DNA survives. I’d guess that — if that were to happen — there would be literally no living descendants of the Iceni anywhere, unless their ancestors were taken as slaves into mainland Europe during Roman times.