No excuse needed.
There are two things that I learnt doing my BSc IT degree that I still use today.
1. The 7 layer OSI model
2. How to research / search
Google does still support some rudimentary Boolean logic in search terms, and knowing this, as well as using site:www.acme.com search term can get you very quickly to the right answer
Even as an Apple Genius, you were taught to use the very excellent Apple Technician Guides to diagnose and fix problems. After watching two of my ex colleagues literally replace every component of an iMac only to have it fail POST, a quick shuffties of the Technician guide, replacement of RAM with known good, and up it boots.
RTFM will outlive nearly every technical mantra there is, apart from turning it off and on again.