> On the other hand, writing code that the most junior in your team can understand leads to mediocre code.

Disagree on a couple levels. First, while the overall architecture of the system might be complex, there shouldn't be any one single function that isn't readily readable by a junior new hire. Complexity is in the system, there should be no complexity in small sections of code.

Second, the ultimate level of mastery is to be able to build simplicity. Any newbie can write a convoluted mess that nobody can understand.