Why aren’t the old Apollo designs being reused for a moon landing? (by either the Americans or the Chinese)

If you want to address this question, show him some videos about Boeing and Airbus and how they can’t bring back airplane models they stopped production on because of massive supply chain issues. See if your friend is willing to accept that they can’t bring back the 747, for instance.

If this is a problem for aircraft, it is likely also a problem for spacecraft.