The problem is class based components have to be written very carefully to remain testable, and the average developer is not that careful. It's basically a foot cannon, and the worst react spaghetti I've seen has always been a result of huge classes that manage way too much state. I believe that making it a convention for developers to break up their components into small, pure functions will raise the quality of most react applications. Recompose has made this possible for a while, but most react devs aren't familiar with it, and baking it into the framework should make that approach less exotic. Of course, you will still be able to write huge functions that manage too much state, but I think classes encourage this more than functions.