> We know that the Inca didn't build Sacsayhuaman because they said that they didn't.

Where are you getting this from? The Spanish chroniclers report Inca tradition that the 15th century leader Pachacuti initiated the building. The wiki article has a few long excerpts from Pedro Cieza de Leon's Cronicas del Peru, including details of how many labourers were involved and some of the methods for quarrying, transporting stone, and construction:

https://en.wikipedia.org/wiki/Sacsayhuam%C3%A1n

Pounding stone seems reasonable to me. Obviously I don't have any proof or even strong evidence but I saw a video that changed my perception of what is possible. It showed two old men making a millstone with hand tools: https://www.youtube.com/watch?v=lscs5ZgNQrE. The amount of labour involved and quality of the finished item was astonishing to me. Maybe you'll think that the hideous amount of labour needed to make a simple geometric shape makes you even more convinced the Inca has some other way to achieve their even harder task. But it is a fun video anyway.

Similarly astonishing to me is that Michelanglo's David was carved from a single piece of marble with a hammer and chisel. I mean, just look at it: https://en.wikipedia.org/wiki/David_(Michelangelo)

How about you actually read the article, which directly addresses these claims?

You know, if you'd actually read the article you're commenting on, you'd know that both of these things are discussed extensively. But easier to just spew nonsense in the comments I guess.

you can replicate a dressed stone edge with ordinary clay, then dress another stone to match the sample, cmon man

Is there a counter-theory?

This is just baseless brainrot conspiracy claims.

The older construction is also very easy to distinguish from the Inca construction. And the Inca themselves know this history in their community. Brien Foerster has a lot about the Inca culture. https://www.youtube.com/@brienfoerster/search?query=inca

The older construction is made of very big stones of hard granite, that fit perfectly together. Assuming they had some concrete, it is easy how they were able to make them fit so perfectly. If you have a source of materials, concrete is not difficult to make. See https://www.geopolymer.org/

People were not stupid, and technologies were invented and forgotten. And just like Roman technologies were lost in the middle ages, this building technology was lost to the Incas.

The Incas build their houses and temples on top of the existing ones. They used smaller stones that did not fit well together. Still a great culture, but with different technologies.

South America has a lot of cultures that disappeared. They had no written history and a lot of stuff was destroyed by later cultures (including the Spanish). So it is impossible for historians to get it right.

For example there were also people with elongated skulls and red hair in Peru. Could be a result of inbreeding as they also had some other physiological differences. Maybe exterminated by another tribe. https://www.youtube.com/watch?v=5dfpLN3FbQs

History is often full with conflicts, but presented as if it is all known. There are often conflicts with engineers who point out different technologies used for buildings and such. These technologies do not fit in the simplified timeline of mainstream history.

This difference in technology is obvious regarding the extremely accurate Egyptian granite vases https://www.youtube.com/watch?v=7BlmFKSGBzI and granite boxes.