The way archeology keeps pushing technologies and supposedly advanced capabilities "back" in time and genetic testing is showing that supposedly sub-human "species" (e.g. Neanderthal and Denisovan) were in fact interbreeding with "humans", I think the whole paradigm of primitive-to-advanced progression (e.g. the oldest known written languages are actually as or more sophisticated as modern languages) is crumbling in the face of realities. And I am in no way suggesting Von Danikenesque Chariots of the Gods fantasy.
I agree.
Humanity 'grows' in fits and starts, with periods of regression.
The most choice places in the Western Hemisphere to build civilization were either subject to volcanoes, were flooded as the ice melted (coastal enclaves), are buried under river silt and later development (inland river confluences). Few places were stable enough over the past 12,000 years in terms of climate or geography/geology to preserve the remains of any advanced civilization, and the whole Darwinian thought pattern that permeated Archaeology and Anthropology was heavily colored in its outlook by the assumption that 'modern' humans are the most advanced (and thus blessed by whatever logic to loot and otherwise exploit those 'primitives').
Yet if you could have the hypothetical civilization truly living in harmony with nature, would it have developed the technologies industrial man did in pursuit of food, resources to feed industry, conquest (because even 'primitive' people want to keep what's theirs), and the desire to work less and do more?
Quite possibly not. Many of our trappings are born of finding solutions to hardship, to defending against being looted and enslaved, or to loot and enslave, often in conflict over resources.
As humanity works its way into an era when fewer people actually do the heavy lifting needed, and things become more centralized seeking economy of scale, the hubs of identifiable industry diminish in numbers and as such, there is less in terms of enduring 'impressive' artifacts to be left for the future. Much of what has been has been recycled, and like a burnt out castle tells us little not told by ash layers, rubble, broken dishes, and the expended projectiles of conflict.
In archaeology, the trick is to locate sites and discover enough puzzle pieces to get a coherent picture, but with enough missing, you'll get the beach, the waves, but not the sailboat.
In Anthropology, the further interpretation of those artifacts to paint that cultural picture is done with a palette colored by the bias of the interpreter. Entire aspects can be missed, or misinterpreted because of that. Thus the benches near the public toilet could be interpreted as an object of 'great religious significance', the path to the beach part of some ceremonial recurring pilgrimage, while something truly held in awe and esteem might not get any notice because few actually went there.
(That doesn't mean that it isn't intriguing and fun, especially when the lack of apparent written language opens the catalog of artifacts to wild speculation about the culture involved)
But in coming up with anything valid, it must be remembered that these were
humans, with all the desires, motivations, foibles, and virtues of any other humans, all subject to the almost immutable catalog of behaviours and motivations we call Human Nature--regardless of the technologies that were means to an end, and more rarely, an end in themselves.
I honestly think that is the thread to follow back in time to trace our roots, because that is indeed what makes us "human". When signs of that human nature are no longer seen, then we have gone back to what came before mankind.
