The Sino-Tibetan language family is rather large with around 450 languages (making it slightly larger than the Indo-European family by some counts). Within the Sino-Tibetan family you have the Tibeto-Burman family, which has around 430 members, making it a disproportionately large sub-family. The other 15 or so languages are in the Chinese family, which are those heavily isolating languages, but the majority of the Tibeto-Burman group are relatively agglutinating. Many of the Central Bodic languages I work on have at least affixed tense, aspect, negation, plurals and case marking.