Let's go back 6 years in webdev land. jQuery was king, Angular was the up-and-comer. You have a fairly complex jQuery site probably rendering most things from ruby or php. The only way to debug it was with console.log and refreshing the page.
Angular comes around introduces modules and unit-testing, cool! You hook up grunt and protractor, you install angular batarang. Everything is good. But you end up building this huge angular app. You try to debug this edge case when you have this panel open under this tab. You get frustrated that you have to click on the same things over and over again. Livereload can inject css but not js. When you change the html of your angular directive you have to reload the page too.
This is where React comes in. React + Redux + Webpack makes it such that you can apply livereload to _everything_. The css that your component imports, the html it renders, what actions happen when you click a button. Everything. It's not necessarily the new shiny rather than just the next step to making things easier for devs. It gets out of your way so you could focus on styling, structure and business logic.