"Shigley's Mechanical Engineering Design" is a great textbook if you want to learn the most you can with the fewest books about designing mechanical structures and moving parts from a strength perspective.
Fluid flow/ thermo would be the other main academic area that this book wouldn't cover.
There's a bunch more topics though that you build over years of intuition- manufacturability, design tradeoffs, etc.
Is there a "mechanical engineering for dummies" educational path (Book? Software? Kit?) that would equip someone for doing like 90% of the mechanical design&prototyping work?
Interesting point: "when you solve one bottleneck you find a new one somewhere else."