Flux/React are actually quite simple and I can put the core architecture together in under 50 loc of Elm.
You will always have to deal with complexity, it just depends on what kind of complexity you are willing to stomach. Some people prefer to deal with the complexity of stitching things together, other people prefer to have things stitched together for them and deal with the complexity of many abstractions. Both are fine choices, and we will debate endlessly with each other over which approach is the best approach. (hint: neither are).
React is also pretty simple when compared to libraries like Angular.