The wasted time and money in construction comes entirely from two places: a small percentage of crooked builders (and their local council mates), and the bureaucracy that is trying to protect the citizens from same. Big brother puts in a lot of hoop-jumps standards and supposed checks and balances that end up creating massive delays and costs for the consumer, but the actual standards (while usually quite sensible) are easily sidestepped by the crooked builders, so the war continues, and the overhead constantly increases with the usual expansion-only government regulation ratchet.

None of these things are susceptible to "AI" and other such automation. We have had prefab construction for decades.