Well, new words _are_ helpful in compressing complicated ideas into smaller spaces. But no matter how complicated the concept expressed by a word, it _can_ be uncompressed into more words by someone who understands it.
Of course, not every environment is for teaching. I’m not criticizing standardized language: it serves a purpose as it can speed up communication. But when I say “forget the special words”, I’m speaking of opportunities to teach: If you can’t explain what you know to someone who knows less by removing the specialized language and utilizing plain speaking instead, then one’s knowledge of the topic is less than one thinks.
At the same time, not everybody is capable of teaching so I suppose I shouldn’t be _too_ critical. But I take Feynman’s words to heart. I read them long ago and they inspired me to continue striving to be able to “explain anybody to anybody” when necessary and I seek out opportunities to do so in fact: it’s a fun challenge. That’s when I discover whether I REALLY understand a topic or not.