"The team say tthe discovery of Caer Caradoc, a pre-Roman British city is a severe embarrassment to academics who take no notice of Welsh records."
Why do academics ignore Welsh records?
Probably the same reason why they ignore biblical records as well. Because, in their mind, "It can't be true."
For Welsh and biblical records, the academics say "This can't be true!"
But, most academics add another comment on the biblical records.
In private moments, they pray "This had better not be true!".
We have a similar problem in the United States. Although there were something like 30 permanent settlements on what is now the US East Coast by 1600, we only research and study the later English settlements at Plymouth and Jamestown.
Victors write the history. Traditions of defeated people get turned into "myth" anytime they are in conflict with "real" history.
The oldest surviving Gothic Bible is dated to about 350 AD. Goths are believed to have originated in Southern Sweden & they were a Germanic people. History books say Charlemagne "Christianized" those "barbaric pagan" German tribes.
Back to Wales. Welsh built stockade type forts & they retreated from them when necessary to survive. They'd attack parties trying to forage from the locations of their former forts. The Welch long bow was useful for this, so attackers found staying is Wales unattractive.
Romans built stone fortresses along the Welch coast, so I have to think that digs along the coast that look like permanent settlements would have to be from the Roman "occupation", though they would be upon older Welsh settlements. Get deeper into the heart of Wales, a defeated people's last stronghold, purposely inaccessible, built of wood becomes a "mythical" place pretty quickly.