But you can't really knock it down unless you have something to replace it with.
The pyramids are there and they got there somewhere. People came up with theories based on all of the evidence they had.
If you want to replace those theories you have to present better ones.
I honestly think the biggest problem that is super obvious is that the great pyramid wasn't built as a tomb for Khufu based on the evidence at hand. When it was built is completely based on who they believe built it, which itself is based on extremely shaky foundations.
I believe I have stated this prior in the thread, but the story about the Great Pyramid from the orthodox viewpoint, was created during the late 19th/early 20th Century with regards to who they thought built it and when. And when you look at the evidence that was based on, it's silly. The Khufu attribution is based off of 1 small statue of Khufu that they found, as I recall, in a nearby mortuary temple and a cartouche that means something along the lines of "khufu's gang", or something to that affect. The great pyramid is not inscribed otherwise, and is never referred to directly in any contemporary or reliable source as built by or for anyone in particular. It's a complete guess.
THE ONLY REASONS the great pyramid itself is attributed to Khufu (outside of my final thought below) is described in the above paragraph, and the only reason it is given a construction date of circa 2600BC (and a 20 year time period) is because it had to have been built during Khufu's lifetime for it to be a tomb. It, along with the other 80 or so pyramids found in Egypt, have never, not one instance, been found to have a burial contemporary to construction, found in them...ever. I don't know why people seem to confuse the valley of the kings with the pyramids, but that is where the burials have been found (yes a few have been found near or in pyramids too, but not contemporary to construction, even the given dates for said construction which is likely incorrect in most cases), and it is many many miles away from Giza.
Last, because there really isn't much to go on, there is a big habit in archeology and in Egyptology in particular (by default because it is the most widespread and well preserved archeological landscape on the earth due to climate conditions) of attributing structures of unknown origin to the same entity of nearby structures of known origin. IE, "Khufu built temples/buildings near the Great Pyramid, thus, Khufu built the Great Pyramid"...it's really REALLY faulty logic but taken as gospel in Egyptology.