I'm not criticising the idea or the framework, but the react team have had to go to enormous lengths to make that one simple idea work. And the community have had to embrace (and then sometimes, forget) some pretty controversial techniques and concepts in that time, with more big changes coming soon (hello concurrent mode!). It has cost FB tens of millions of dollars to develop. I'm not saying that investment hasn't been worth it, but peek under the hood and the complexity is huge.