One reason why archaeologists reject the idea of ancient advanced civilisations is the lack of evidence. Consider however that since the last glacial maximum roughly 20,000 BP, sea level has risen some 200 to 300 feet. Next consider that almost all major cities in the world currently are at less than this height above sea level; people like to live on the lower parts of rivers with flat land and near the sea for trade.
Next consider that as sea level rises, progressively higher land becomes the coast, which in bad weather is pounded by crashing waves. Where the sea invades land. such as on the East coast of Britain that is tipping down, almost nothing survives the battering of waves. The evidence for these very ancient civilisations is most likely under the sea, and all that will remain are the most massive constructions.
This should be considered when reading about those underwater places that have been found with hard to explain formations, such as those described in Graham Hancock’s Underworld.