In your heart you'd prefer to stick to Oldspeak, with all its vagueness and its useless shades of meaning. You don't grasp the beauty of the destruction of words. Do you know that Newspeak is the only language in the world whose vocabulary gets smaller every year? ... Don't you see that the whole aim of Newspeak is to narrow the range of thought? In the end we will make thoughtcrime literally impossible, because there will be no words to express it.
One thing I think people don't get about language, maybe the biggest misconception English speakers have, Orwell included... The size of a language's vocabulary is not the same thing as its expressive power. In fact, the two things may be inversely related. What really gives a language expressive power is how freely, logically, and consistently its small pieces can be combined into larger ones. As you might imagine, the more pre-built words you have, the less demand there seems to be for clear, productive word formation rules. But as soon as you want to express something there's no English word for, you might get a little tripped up having to use a whole sentence or two to make sure you're understood, which interrupts the flow of your speech or writing. So most people just find a rough equivalent to what they were trying to communicate and move on, generally without even noticing. (When you study a very different language like Japanese, by the way, you notice a lot of really useful things that aren't so easy to say in English.)
Most of our ability to create new words comes from Latin, actually. You can coin new words (or neologisms) pretty easily by following the word formation rules of Latin and using Latin roots and affixes. Scientists make extensive use of Latin in this way, but most everyone else won't feel comfortable using a given word unless they know it's listed in a dictionary somewhere, regardless of how clear the meaning is. New terms built from Germanic roots (such as "Newspeak") sound silly and childish whereas new terms from Latinate origins (such as "neoloquium") sound stilted and technical (and most people aren't literate enough to figure out the meanings very easily anyway). This uneasiness with new words is particularly prominent in English, and it actually makes clear communication in "Oldspeak" problematic.
Sure, the relative inflexibility of English word formation can make it difficult to express certain things from time to time, but an even bigger problem is all the connotation that gets attached to the words we do use frequently enough that they "sound right" (and not highfalutin or otherwise weird). A good example is the idea of "paranoia". If you say somebody's "paranoid", you're not only saying they think people are out to get them but also that the paranoid person is mistaken. What's it called when the paranoid person is right? Justified paranoia? Not really, that still implies the person is mistaken, just understandably so. If you're goal is to make thoughtcrime impossible, words like "paranoid" are a good start.
It's interesting to note that Orwell's Newspeak, which was designed to limit the expressive power of English, actually turned out to be really useful in labeling some ideas that weren't particularly easy to communicate in standard English: thoughtcrime, doublethink, unperson, etc. That's because he not only simplified the vocabulary of English but also simplified (and clearly delineated) its word formation rules. The way to limit expressive power is to eliminate or obscure virtually all word and sentence formation rules, which means you'd need quite a number of atomic, unanalyzable words to talk about anything.
If you could just extend people's attitudes about coining new words a little bit to make them uneasy generating new sentences they've never heard before, you'd really be controlling their minds. But that kind of language would look nothing at all like Newspeak. For one thing, almost every sentence would consist of a single word. Lame. Right?