English has the broadest vocabulary of any language. It allows precise expression of specific ideas, and if you don't have the finest possible word or phrase at your disposal, it is quite acceptable to purloin the words and phrases of other languages.
Language is about the transmission of ideas, not words. Having a large vocabulary allows you to use less words to convery more ideas. Also, while a word like "mellifluous" is quite superb, if you surround it with other, equally superb words, you diminish it. Adjectives and adverbs will not reduce the blandness of your writing. You're very obviously polishing a turd when you have to haul out the commas to form lists of descriptors.
Florid copywriters make frequent use of a thesaurus, but they've never read a book.