lesslucid

Mr Ghosn, your campaign seems to have the momentum of a runaway freight train. Why are you so popular?

Business idea: assed chaps. For the novelty!

Anything can be said in any language; that's part of the nature of language. I think the feeling of freedom comes from the naturalness and regularity with which various ideas can be expressed.
Two quick examples: some time ago, I was trying to work out how to say the English expression "world-weary eyes" in Spanish. The construction of phrases in Spanish doesn't work the way it does in English so you end up having to say something like "eyes that are weary because of the world". It's the same meaning but the cadence is totally different.
Think of all the funny not-really-words that exist in "Whedonspeak", as in Firefly Cpt. Mal says he's going to do "captain-ey" things. We're not allowed to say "captainey" in correct English, but what other term would you use to express the idea of a collection of activities that are related to each other only by their association with the concept that "captains do these things"? Of course there's a more long-winded way to express the idea of being "captain-ey", or you can just go ahead and use the "wrong" term (which will be fine in some contexts and embarrassing in others), but wouldn't it be good if there was a language which had a completely regular, reliable, and universally available way to turn nouns into adjectives? You wouldn't have to fumble around for the words to express "captain-ey-ness" because, so long as you knew those rules, you'd be able to express the idea in a concise and correct way.
Of course, there is such a language: Esperanto. :)

Uh, Arkham Horror is midlevel? I'd hate to see your idea of complex...

The problem with English is not that it's inflexible, it's that it's irregular. A person who studies physics is a physicist. A person who studies biology is a biologist. A person who studies chemistry is a chemist. Imagine you're learning all this as a foreigner. You've learned a rule, right - there's a principle at work, so you can start working out what some other words are going to be: a person who studies plants will be a plantist. (Oh, a botanist?) A person who studies animals will be an animalist. (Zoologist? Huh?) Uh, I heard someone being called a Marxist the other day, they must be someone who studies Marx? Oh, not really? And a racist - they study races, I guess? No?
There's plenty of flexibility and creativity in the way that English is used, but the trouble is, in order for a "new entrant" to join the conversation, they have to be walked through all of the steps that led to the terminology we have now. You hear that someone is an oncologist - it only makes sense to you if you've already had the explanation of what that is. Whereas, for an Esperanto speaker, if you know the word for "cancer", then you also already know the word for "medical specialist in the area of cancer", because they share a root. In Esperanto there isn't a single suffix denoting "person who studies x", "person who believes in x", "person who works in the area of x", and "person who has irrational prejudices about x", where the only way to know which one the suffix means for any particular word is to just "know it already".
"Freedom and creativity" are often thought of as being able to "escape from all the stuffy rules imposed on you by others", but it's a misunderstanding. Good rules promote creativity by releasing you from the obligation to waste your time working out all kinds of petty and unimportant things that should have been done according to some system, but weren't.