This book is a collection of universal ideas for software development. The whole idea is to lay out "laws" for developing software, to improve code quality for future programmers.
Everyone is a Designer
But nothing can be built by committee. Decisions are made by one person alone, with seniors having veto power over design choices. Be empathetic if you override someone, tell them why. You won't have to as much in the future!
Developers have to have autonomy to solve problems to learn and grow!
Why is Software?
Software is written to help people. It's pretty boilerplate design and business advice, but understanding why you're writing that code informs your design, and makes for better code. Motivation matters!
This user empathy should guide planning too. Ask how a decision will help your users, and prioritize work that helps the most users the most. If it wouldn't help users, mark it off the feature request list.
Remember that your software's purpose isn't to make money. It's to solve problems. Money is rad, but if it's the only reason you can think of that you're writing that code, it probably isn't worth it.