> I don't understand what problem they're trying to solve
I don't use React. I learned a little bit of Vue. I'm definitely not an expert, but I think there are (at least) two problems that they solve: consistency and reusability.
Consistency: I think the hope is that if you're a React programmer and you see a brand new site written in React, you'll understand it, whereas if it used vanilla JS, it might be written in any number of ways.
Reusability: if you start writing your own reusable functions in vanilla, you'll eventually build your own React -- it's the build vs. buy decision.
I don't use React. I learned a little bit of Vue. I'm definitely not an expert, but I think there are (at least) two problems that they solve: consistency and reusability.
Consistency: I think the hope is that if you're a React programmer and you see a brand new site written in React, you'll understand it, whereas if it used vanilla JS, it might be written in any number of ways.
Reusability: if you start writing your own reusable functions in vanilla, you'll eventually build your own React -- it's the build vs. buy decision.