Knowing a language or a tool doesn't mean you will always know the best or the smartest way to do something. This is not necessarily a test of your programming ability. And best practise is more often ever changing. Almost every language or tool is always ever changing and improving itself which best practise also keeps evolving.
Secondly you don't necessarily need to know or master a language or tool for every kind of work. You can just choose to learn as you go along with it, in which case knowing how to search and use the most effective way to do something is very useful.