What happened to kit homes and plan books? Rather that bring down the cost of custom design, can we bring down the cost of partially pre-fabricated, modern code

What happened to kit homes and plan books? Rather that bring down the cost of custom design, can we bring down the cost of partially pre-fabricated, modern code-compliant homes that still resemble something traditional (not a shipping container home)? That said, I think this is neat because I’m buying a condo and knowing what’s even possible (physically, allowed by code, etc) seems more art than science. Getting answers usually involves bringing someone on-site, and almost nothing can be DIY’d anymore (either due to permits, HOA, complexity, etc)