Definitely this. This is an interesting talk, most thing shouldn't be shiny. It's not about stagnating of course, but you should think more than twice before adding a new technology to your stack. Mastery is when you know everything that's wrong with a piece of tech, before that keep in mind the amount of unknown unknowns and the cost of exploiting something new.

This nicely goes in depth on the five domains to look at to know where you stand as a manager. Also proposes action to increase the impact. Good food for thought.

Interesting points in this article. The exact definition doesn't matter much. What really matters is the common understanding within a team of what technical debt is. It's also a good idea to be able to link it to actual money and business impacts.