If everyone was committed to living in the best interests of this world (physical and social), there would be no need for government (ignoring the sad reality that the numbers of people are so inclined seems to be decreasing). Or would there? Even with the best interests of the world at heart, people are going to disagree on all sorts of things. That's not because we're bad - it's because we're all different. That is good - imagine the world full of people all the same - but it makes consensus difficult (even the Animal Farm type of consensus currently in vogue).
One of the big issues with people living in communities is that we differ on what's "best". You only have to look at recent news to see people evenly evenly divided on issues such as Brexit and Trump. Churchill said democracy is the worst form of government except those that have been tried from time to time (although he borrowed that saying from an unknown predecessor). Personally I suspect it might be improved by raising the bar so that changes can only be made with say 70% majority - but even decisions with 90% support can still turn out to be poor decisions so that is at best a patch. But at least it should hold politicians more accountable.
Even when those leading changes are honourable, and the changes are honourable, the changes will still be corrupted. Power corrupts. And over time entropy degrades things, so left on their own, everything moves downhill. The introduction of our state welfare was world leading - but I doubt those responsible foresaw the state dependency and associated problems it led to. Those who worked at administering welfare used to see their job as helping those who needed it. Today the starting point is to minimise what people take from the system. Similarly look at the rise of an institution such as school. That is complicated by some of the pioneers seeing it as a tool to mould and control society. Even so the aim is still supposed to be about education. Front line staff do their best - but the system is focussed on a number of distracting tasks.
Because there is seldom an absolute "best", governments should have a minimal role in society - otherwise we inevitably live with decisions that are good for some but not others - at best mediocre. It's sad that we so seem to regard that as the best option. And that doesn't even take into account the system or personal biases for or against some people. To be clear I'm not saying this of any party in the current system. They're all such a pale imitation of "government of the people, by the people, for the people" that I've personally never been able to vote blue or red. I usually vote against the status quo - a terribly distorted way of voting. That's not to say there haven't been honourable politicians - but even the best seem to get sucked under (or spat out) by the system.
If we agreed the government should be restricted to basic functions, the principle still leaves such a lot of details to be sorted out we'd never reach agreement. Even if we did, what's basic in one situation wouldn't be in another. That's why I have seldom been motivated to even demonstrate, let alone get involved in politics.
Early in my career I wrote a scathing report on a government computer system I'd come back to help implement. My boss toned it down and gave it to his boss. He toned it down and on it went through three more layers before it went to parliament. Next I heard a speech by the Associate Minister of Finance of the day, saying what a great system we had. The politicians and their helpers were motivated to get good news out about government computing to counter the health computing fiasco they'd just been through. No one lied. They just made the information they received sound a little more "palatable"..
There are people who work towards improving the system. I wish them well - but don't expect the broken system to be fixed while those able to fix it are part of the system. And based on history, i don't think a revolution would solve things. Instead of trying to change the system, I believe the best we can do is to each change our little bit of the town, country and world for the better - not just as a one-off, but as a lifestyle.