But the opposite is not true, i.e a world without monarchies would not necessarily be a "just" world. Look at France which abolished it. Look at the USA which never had one or, rather, has an elected one since the US Constitution is a democratised version of the 18th century UK constitution with the Senate as an elected House of Lords and the President as an elected King (and Trump doing a good impression of George III). A "just" world would be a world without states and heads of state, whether hereditary or elected.