Modals: https://reactjs.org/docs/portals.html
Or animations (in react-native at least, but if you click the link you'll see it works for the web just as well): https://www.webpackbin.com/bins/-KfKys3S2mgEH9UsE8GL
In Vue you're pretty much in the rain. The community isn't encouraged to explore due to half-baked-in solutions, and baked in stuff in general is browser-complacent and thereby very limited. So you get css class animation groups (=react-animation-group), state is a one trick pony tied to the lib, theming isn't considered. There are so many open gaps and holes in the eco system at large, i'm scratching my head over how this would possibly be a plus or easier to the developer. It is often not.
Re. animations, etc., those aren't too hard with lifecycle methods, which, if I understand correctly, Mithril copied from React.
And while React is simple, you quickly have to add a router, some state management etc., so instead of a small simple library most React-projects I have seen end up being a custom framework.