There isn’t any divine mandate that enshrines universal adult suffrage as the only right and proper way to select delegates and resolve issues. Indeed, among major religions, I cannot think of a single one which even mentions such a system in its scriptures. Neither Britain nor the U.S. had anything like universal suffrage in their formative periods, and neither granted the vote to women until the 20th century. The U.S. Constitution is a grab-bag of anti-majoritarian mechanisms, and almost every U.S. state constitution contained anti-majoritarian representation intended to prevent rural areas from being dominated by the iniquitous hives of villainy that are cities until this was swept away in the 1960s by the supreme court under the made-up doctrine of “One man, one vote”.
There are a lot of ways to organise representative government, many of which have been explored in libertarian science fiction: some based in history and some innovative and based upon new ideas and technologies. These might include property qualifications to vote (as existed in the U.S. and Britain for many years), restricting the franchise to net taxpayers or scaling votes by the voter’s net contribution to the public fisc, direct democracy where individuals could assign their vote to a proxy representative who would exercise it (with proxies being revocable at any time), with or without the ability of proxies to be bought, sold and traded. Votes might be given to all citizens, regardless of age, with parents having the right to cast the votes of their minor children (this would probably increase the stability of the society dramatically). One of the planets in Karl Gallagher’s Torchship novels is a pure plutocracy where seats in the legislature are auctioned to the highest bidder, which has the unexpected consequence that the society is largely run by guilds who combine dues of their members to buy seats to represent their interests.
Now, many people may not be able to imagine that any such radical change could occur from the present system, but who in 1900 imagined direct election of senators, or in 1950 abolition of regional representation in state governments, or in 2015 mass mail-in voting with no effective voter ID? When something isn’t working, it can be changed, and when change happens, it can be faster and greater in magnitude than many imagined were possible.