What does it take to be technically competent engineer?

Looking at this thread [0], one can notice how a competent engineer has skills both managing business and understanding technical issues. The post also discusses on why many juniors do not have enough experience on technical side.

Therefore, can you suggest/point out the ways one can be technically competent to that level degree?

From my experience, study alone doesn't suffice. Because one cannot remember all the technical details from textbook or paper! And if we do not implement new things, we are unlikely to understand things completely.

[0]: https://news.ycombinator.com/item?id=30574489