This is more of an XKCD fan boy project. So let's look at a famous XKCD comic using this, "US Space Team's Up Goer Five". "US Space Team" barely makes sense, does more to obscure than illuminate, and "Up Goer Five" makes no sense at all.
First off, there are many dimensions to reading new languages. Nobody is saying "learn 1000 words of English and you're done for life". Rather, achieve fluency in a subset, then work on becoming more idiomatic. If you're lost somewhere and need help, nobody cares that you sound like a stupid child. (They probably won't notice, though. I've found through learning other languages that rare words are actually very rare and of extremely limited use. Obviously if someone uses it and you don't know it, you're stuck. But you can get by without it.)
US Space Team tells you what NASA does. NASA on its own tells you nothing about what they do, for all you know it could be the National Agricultural Sabotage Administration, and their goal is to blow up farms.
You have to separate language out into the multiple dimensions that it encompasses in order to understand certain aspects. It's clear to me that you use language as a social signalling method, "that person doesn't know what NASA is, hah, they're dumb and I won't associate with them as a result." That's fine, but there is another aspect: explaining ideas. And that can be done with less than the full set of all English words.
I welcome simplified English in every shape or form, from limiting words to changing spellings and streamline it. Its no more language of people from England, every one in the world has stake in it. English reformation is long over due.
Some people insert heavy hitter words into their speech in order to sound more intelligent. It comes across as unnatural and awkward, though.
But people who have acquired large vocabularies organically, by being around people who talk that way or by reading a lot, use it naturally and unthinkingly. And then there are authors and such who use language like a painter uses color. English is a very rich language, and if you want to paint a rich scene with words, there is quite a palette to choose from. Would you tell a painter he can only use primary colors?
Unless you meant all children are stupid....