The path to becoming a good design engineer ?

Learn how to learn.
If there is one thing I want to teach others it’s this: Not all learning can be obtained from an instructor in the classroom. Once you get out of school there is still a lot to learn and you have to develop a discipline of reading and studying manuals and books on your own. Don’t ever think you must take a class in some subject to become proficient in that subject. It takes practice and dedication to learn a new subject on your own but it’s a skill that will pay huge dividends. My most valuable skills were learned on my own.

Maintain your curiosity
If a subject interests you, then spend your off time studying and learning about it. Expect to spend significant time outside of work learning about things that might someday become useful at work. Even typical hobbies have a way of paying benefits at work. Following my own natural curiosity has led me down some very interesting paths. I learned a lot along the way.

Have fun
Don’t do everything with the expectation that it will generate income. Some things must be done for the pure pleasure in it. Don’t ruin a hobby by turning it into a money making venture! However don’t be surprised if opportunities to generate income arise. I have developed significant passive income from my 3D printing hobby by selling the designs that I did for personal pleasure.

On CAD
Don’t confuse knowing CAD with being a designer. They are not the same thing. CAD is but a tool. A good designer can produce workable designs without ever knowing CAD. Knowing CAD is a necessary tool to have at your disposal these days but I want to emphasize: knowing CAD does not make you a designer. Just like knowing how to use a hammer doesn’t make you a carpenter. I have witnessed a great many here on GrabCAD that are making this mistake. Freelancers advertising their impressive CAD skills with no mention of their design capabilities. You know CAD, Great! Now learn how to be a designer.

I totally agree with Bob, and even often use the same examples when it comes to talking about "technology (tools) versus science (knowledge)."

I would add that “design” is made up of two important elements: idea generation and idea evaluation.

The generation of ideas can be an innate facility (natural creativity) and/or have a certain degree of systematization and training (such as learning lateral or divergent thinking). But it is just one of the steps to create a good design.

The other vital element is purely rational (derived from vertical or convergent thinking): the analysis that tests the ideas generated to determine (qualitatively and quantitatively) to what extent they fulfill the useful effect expected of them.

There are certain designs that can be executed primarily creatively and do not require "rational validation," such as designs in which beauty is the goal (architectural, musical, plastic, etc.). But in engineering, in general, the rational component is very strong and one must seek the ability to "test their design" against the many phenomena that could affect them, such as: kinematics and dynamics (motion and forces induced by the same); statics (resistance, rigidity, stability); the impact (rapid application of loads); vibrations (modes and frequencies of natural and forced oscillations); fatigue (accumulated damage from cyclic loading); friction (effects of wear); heat (possible influence on the integrity of the materials); fluids (mass and energy transfer mechanisms, heat transfer, etc.); and many others!

For this reason, I suggest that you balance your knowledge between ideas generation and their evaluation. In this process, TECHNOLOGIES ARE A USEFUL BUT NOT ESSENTIAL TOOL: no tool defines an engineer (although it can help them a lot).

Greetings