The real problem is in how we set up the governments. We give to much power to a few people.
What we really need to do is let people vote on individual issues. Want to go to war that will affect everyone and will cost trillions? Let's have a vote.
I live in Belgium, a country where 3 million people are paying for 8 million others. Those 8 million include kids, people without a job and people in retirement or who got sick. And we should help them. But it also includes 1.3 million government employees (hundreds of thousands more than The Netherlands where they got 6 million more citizens), people who aren't really sick, people who aren't willing to work, people who retired at an age way below the average European retirement age.
So they want the system to continue even though it's unsustainable. When asked, they aren't going to vote against a system they are taking advantage of.
Unfortunately, people who are in favor of things like universal healthcare, minimum income, etc., fail to appreciate that good intentions don't always lead to good outcomes. (I'm speaking about typical HN readers who support these things who won't personally immediately be getting a piece of the pie.)
As you say, the fact that people will vote for things that are in their self-interest at the expense of the society as a whole is a problem with democracy. In the US this has traditionally been avoided by a strong sense of patriotism / nationalism and an ideology of individual responsibility, but these barriers are eroding with cultural changes, increases in minorities with different values, a dysfunctional education system, and various economic disruptions.
If a minister is weak, he will end up acting (unknowingly) as the de-facto press officer for the department. In any case, we end up electing representatives, not delegates. Our power to influence policy starts and stops at the ballot box (actually, we have rather more power than that through MP's letters & party policy groups - but for the sake of argument we will ignore these).
Indeed, even in systems with impeccable democratic credentials, decisions end up being made by relatively small numbers of individuals; individuals that can be effectively lobbied, influenced or coerced into making decisions that are not in the best interests of the nation, or of the people.
We need a technological solution that will help facilitate a general broadening of participation in the legislature. Universality is unrealistic, but open and broad participation is both achievable and realistic - Why should we limit government to a small fixed number of permanently employed elected representatives? Why not a larger, more flexible group of part-time specialists, each participating in only one or two issues?
But today we have the technology to take a nationwide vote within a day so it is within the realm of possibility.