I have long been known to use big words when speaking English.
Often, I use big words sith they come to mind more easily than simple words. This probably comes from habitually reading things that use big words — such as dictionaries, Wikipedia, and the ramblings of nerds — and maybe a subliminal desire to sound smart. Regardless of exact cause, that fancy words come to mind first does not, in my case, always imply they're better than similar simple words. Most such readily-available words are trivial and unhelpful replacements of the kind Orwell hated, like my use of "characterise", "disregard", or "undesirable" in place of a normal person's "describe", "ignore", or "unwanted", respectively. This is gratuitous grandiloquence.
Often, I use big words sith they mean what I seek to say more closely than their simpler equivalent. Such is the advantage of a language with so many near-synonyms. Sometimes I really mean "principle", "algorithmic", or "traditional" as distinct from "rule", "routine", or "old". Usually (not always) picking such a precise word takes more effort than picking a simple or gratuitously-grandiloquent equivalent. This is justifiable grandiloquence.
I want to keep around justifiable grandiloquence and put an end to my gratuitous grandiloquence. Ideally, you would object to my use of fancy words precisely when it is gratuitous. But it is not necessarily obvious to my readers or listeners whether any particular grandiloquence on my part is gratuitous or justifiable. So close enough to that ideal, and much more achievable, would be to criticise any use of fancy words which is not obviously justifiable. If I also recognise it as gratuitous, I will correct it with simpler words.