They are cut too precisely and fit too well for this to be "simple" mathematics, logs, sand and leverage. Imagine dropping a stone and finding it didn't line up very well. Now you are up Sh*t's Creek. Maybe there are abandoned pyramids that were not coming out as planned, I don't know.
Factor in the intricate passages and secret tunnels and you are looking at an advanced race. Whether the human race was that intelligent in the past and just turned into idiots as time went by, we cannot answer that.
As far as aliens building pyramids to house dead humans? Do we really know what the original function of these structures is? They may have a far more "functional" purpose that we haven't figured out yet. Because termites get into your house and lay eggs, doesn't mean that is why the house was built. It is possible that the reason the pyramids are used for tombs is due to the fascinating things that the early Egyptians observed taking place at them? The "magical" properties and a structure built by a being more advanced than yourself may equal a magical place - and a magical place may offer everlasting life. Isn't it what we all want in the end?
If anyone believes that our ancient ancestors built these structures, developed the secrets of mummification and the advanced hieroglyphic language depicting the future of mankind rather than the past, you should also consider that mankind must be devolving rather than evolving. If we cannot figure out with any degree of satisfaction how we did things in the past with all the intelligence we supposedly have garnered through the years, how can it be otherwise?