People will respond saying you "can do this with React, too". But in practice it's not nearly as nice to do as with Vue. You need React and React DOM AND JSX to really make it practical; writing React render functions is not really what you want to do when you are adding some simple functionality to an existing web app (like form validation).
> simple functionality to an existing web app (like form validation)
If all you are doing is adding a simple form validation to an existing web app, then you only need few lines of plain JS. You don't have to use vue either.
People will respond saying you "can do this with React, too". But in practice it's not nearly as nice to do as with Vue. You need React and React DOM AND JSX to really make it practical; writing React render functions is not really what you want to do when you are adding some simple functionality to an existing web app (like form validation).