There have been many demonstrations of hauling stone blocks the size of those used in the pyramids using ropes, ladders and manageable teams of laborers. And if you can haul them, you can stack them. But I suppose the alien enthusiasts won’t be satisfied until someone builds a full scale copy of the Great Pyramid by this method. I would be happy to take on the job if someone gave me a big enough pot of grant money.
That, of course, does not rule out aliens.
In fact, the evidence for aliens in ancient Egypt is persuasive. The key and irrefutable piece of evidence is the Sphinx. Obviously, only a race with intellectual powers far beyond mere humans — and likely extraterrestrial or from a parallel dimension in origin — would be sophisticated enough to worship the Sphinx.