An autocratic country could easily spread propaganda in the democratic country, because of “free speech” rules that most democratic countries have, but a democratic country cannot easily spread its propaganda in the autocratic country.
An autocratic country can buy an election in the democratic country, but the democratic country cannot easily coup an autocratic country.
Are all democracies are doomed to fail?
Is the future of humanity, autocracy? For the rest of humanity’s existence?
No, representative democracy works when the system is designed to actual require representatives to do that, to represent their constituents. The US does not do that.
Most representative democracies have no requirement for representatives to actually vote accordingly to their voters interests. This is called the free mandate.
So the electorate college works in the same way. I vote for a middle man which I trust to vote accordingly with my wishes. The electoral college is a dumb system no doubt, but it isn’t necessarily non-democratic