I found Velikovski’s books very interesting 4 decades ago. We now have pretty good evidence from Firestone et al that there was a major boloid event in north America and the northern hemisphere that could have caused evidence he mentioned. Things like great tangles of mixed skeletons in northern Canada or Alaska, flash frozen mammoths in Siberia with buttercups in their belly.
I have traveled in Mexico and Central America and studied archaeology and anthropology in Mexico. It is highly likely that the various pyramids there were built by various native civilizations running from about 1500 BC to around 1400 AD. A number of their pyramids are in areas with no mountain ranges. It is also possible that people from Eurasia might have visited and had some influence. The negroid heads of the Olmec suggest to me that Phonecian (sp) ships with Negro mercenary soldiers may have landed on the Mexican coast during the Sea People period (12 to 1300 BC). I can imagine a strong, illiterate Negro warrior taking power there and with his Negro associates taking power for a few centuries. They knew about pyramids and monumental sculpture of rulers. So far as the mountain ranges age, they were built hundreds of millions of years ago. In some cases they are still growing but already well up there long, long ago.
I agree that man has probably had more developed periods than we currently know. We have not explored the sea coasts and river mouths below 300 feet where ice age civilized people would have lived. We also do not know what level of development might have been reached prior to other major ice ages. Primitive humanoids have been found in caves and similar areas, but again, what was down near the sea coasts or below sea level which has probably seen the most destruction or been totally buried by sediments. Much exploration awaits new methods.
The Sea Peoples are a modern invention; there are two references to them in Egyptian contemporary records, which are misdated by centuries anyway. The Sea Peoples left no towns, no distinctive burials, armor, weapons, rulers (including conquerors of the lands they supposedly conquered), written records in their own right, and perhaps most significantly, no wrecks -- the last one being pretty damned peculiar for a massive group of seagoing conquerors.