There is no such a thing as "representative democracy", that’s antinomic bullshit throw at people to lower it down to powerless populace.
Either citizens have the power, exercise it continuously in practice and are supplied with everything it takes to assume that role properly with all the duties it implies, or there is no democracy beyond empty words.
Has such a system ever existed anywhere? How would citizens even have the time?
Switzerland
Continuously exercised and on everything as a matter of course? Not all is done via direct democracy there (even though it is the ultimate backstop in a way), it also has representative democracy.
Switzerland is also a representative democracy
You cannot compare 10 million people with 450 million people when talking about direct democracy. It cannot be done I think. But if you know a way propose it here.
Just saying lets vote directly on everything will put everything on hold until all goes down.
Direct democracy doesn't mean everyone votes on everything.
At the extreme you could do something like localized e-voting: citizens vote on issues that affect a given geographic radius of where they live. Because the boundaries are purely distance-based, gerrymandering is impossible.
Maybe we could have a decaying distance boundary by some measurement like population density or something like it?