> Yeah, but we're not that good at cutting stone anymore

We are pretty good at cutting stone, but not very good at cutting stone with the resources available to the ancient egyptians. So in some sense the technology has been lost: but that's more because there aren't really people try to perfect that craft, as opposed to because of some magical trick or technique that we don't know anything about (Though it's murky exactly what approaches they used, that's because there's multiple plausible ones and it's hard to pin them down, not because there's no plausible ones we can think of).