Somewhat agree. If you really want to understand lean principles, start with the masters of the topic and consider reading some books about Toyota. The first in the list below is a wonderful introduction to how lean manufacturing principles evolved at Toyota over decades. The others can provide more hands on experience on the topic and if you can mentally translate manufacturing principles to software construction techniques, everything will start to make sense.

The Machine that Changed the World

https://www.amazon.com/Machine-That-Changed-World-Revolution...

Toyota Production System Beyond Large Scale

https://www.amazon.com/Toyota-Production-System-Beyond-Large...

The Toyota Way

https://www.amazon.com/Toyota-Way-Management-Principles-Manu...

Out of the Crisis

https://www.amazon.com/Out-Crisis-W-Edwards-Deming/dp/091137...