Do we need a very large vocabulary?
What’s necessary is mastery over the words we already know!
Know the words we know, intimately.
Know how to weave the words we know, magically.
Know how to use the words we know, authoritatively.
Know how to communicate with the words we know, confidently.
When we have such a bond with the words we already know, our vocabulary will naturally keep improving.
How confident are you of your present vocabulary?
P.S. Vocabulary is a matter of word-building as well as word-using.
~ David Crystal