The actual paper is written by archaeologists for archaeologists - just like all papers are written by people in a feild for people in a field.

Your complaint is like complaining that a CS paper doesn't even mention that P = NP is still unknown, and that it just assumes that the best sorting methods are O(n log n). Some things are considered general knowledge in a field, and in archaeology one of those things is: all of this is a best guess given current evidence and methods.

The whole paper is full of citations to other work, which is full of citations to other work - all this work linked includes detailed reports of what was found where and what-else was there, people who do statistical analyisis of similar findings, people who ask questions like "what explanations can there be for it?", more importantly "what else would we find if X was true, if Y was true?". When new evidence arrives, people can and do go back and re-examine these things. Your random skepticism and all the questions you may ask have already been asked and addressed, and frankly: these archaeologist's conclusions carry far far far more believable weight than your half-assed skepticism.