I am an ardent utilitarian. I will always recommend people use as few words as necessary to express their ideas. I also believe that vocabulary should not become needlessly complicated. Sure, it may be nice to have a 50,000-word vocabulary, but if only a couple dozen people worldwide also know what you mean, then you're communicating really poorly (no matter how perfectly that obscure word expresses your idea).
All that said, I do still enjoy my luxury words. I try not to think the worst of people, but my experiences have been that the average person has a weak vocabulary. Words like 'nascent', 'piquant', 'aesthetic', or 'antithetical' go over the average person's head. In my writing, I would not use these words without either describing them within my prose, or expecting (hoping) people will look it up (and in that case, it truly would be because no other word or phrase functions well enough).
There is probably no time when I ever need to use words above a 12th grade level (probably 5th grade if I really wanted to push it), but I know these other words, and some of them I really enjoy using, so I will go ahead and use these words, appreciating them as the luxury they are.
I only have two instances where I make use of luxury words: writing that I do for my eyes only, and when speaking with other people who know the same words I do (or would appreciate learning them). Those people who know luxury words, they're my kind of nerds.