I'm not sure I agree on lack of deadline pressure.
There's a virtuous cycle somewhere if I squint that's fundamentals -> makes it easier to find where the problem is -> makes you more willing to dive deeper -> leads to stronger fundamentals. In parallel maybe, curiosity -> dive deeper reading other people's code / learning about software -> stronger fundamentals
This all leads to things like "I bet this is a network or protocol level issue in this dependency" -> even in someone else's large, open source codebase, I can quickly track down the problem without needing to understand the entire structure, for example. But gaining that ability to intuit takes time, especially for newer engineers.
Edit:
Technically fearless though isn't really the above example for me, it's more, if the business needs it, and we want to allocate resources, there's nothing I can't build or learn how to build in a reasonable amount of time. When you're layers and layers of abstractions up, you're constrained at each layer on what you're allowed to build. Perhaps a simple definition of being technically fearless is the ability to drop down layers of abstraction as needed to solve problems.
I think John Carmack[1] is technically fearless, for example. Known for video games, but I would hire John in any domain and have no doubt he'd be successful.
