Do note that you can use React with much less boilerplate! The nice thing about React is it's very easy to write abstractions on top of it, since it's just a small JS library. For example, instead of writing value/onChange/setState, you can use valueLink={linkState()}. (Note valueLink and linkState were both formerly shipped with React and since deprecated, but it's easy to write them yourself.)
Recently I was looking at my 200Kb app minfied for what was the largest portion of it, and, Lo and behold, react-dom comprised a little under half that size.
Part of this is because React and ReactDOM haven’t switched over to ESM (and still use CJS), but calling react small is probably not entirely honest, at least if you use it like most folks do.
Dan Abramov has said several times that switching React's codebase to ESM won't result in any magic size drops from tree shaking, as there's really not any "unused" portions of the React codebase.
My understanding is that React's synthetic event system is a large portion of its size. Dan suggested that React 16's support for custom renderers would allow creating a "lite" equivalent to ReactDOM [0] if people wanted to, and at least one person has done so [1].
