He's using the subset of familiar technology as evidence that we've not lost it. But there are two massive super-sets that have been lost : (1) recorded & observed artifacts with unknown origins and (2) destroyed libraries and manuscripts

Even in the past 20 years the Iraqi Archives & Mosul Library were destroyed -- not to mention dozens-to-hundreds destroyed since WW1 , as well as many destroyed in ancient conflicts.

"do you think we had anything important in there?" -- "not possible, we've got everything we need already"

In other words, we don't know what we don't know because it's been destroyed and so have our records of it.