UX isn't a true requirement for frontend dev. Tech people (including myself) complain a lot about bad UX, and it's great you're interested but I just want to make sure you're not creating a false idea of dependency there. You can learn how to build UI without understanding the art of creating the best user experience for a problem.
UX is a discipline in itself and it's something a frontend dev naturally learns about over time, and if you value it I say totally learn it! But if you're a backend dev wanting to get into frontend, just get into frontend and get into UX later.