There's probably a reason why modular buildings seem to perpetually be "on the verge", or relegated to edge cases. Usually when a better technology or process is introduced, and it can scale, it's adopted relatively quickly... so I imagine if there were real tangible and consistent savings to be had with modular construction, they would have taken up much wider adoption by now by the bigger players.
Scaling up to be more efficient sounds logical, but I imagine it probably also introduces many new barriers with the growth. There's so much variance with things like regulations, land types, environmental factors, customer tastes, lending, etc....the more jurisdictions and customers you try to build for, the harder it becomes trying to get everyone on the same page. Modularity/standardization already works great in parts or for certain tasks/items, but it seems like a really hard thing to pull off holistically at scale.