Some random thoughts, I hope they're not
1) You don't have to think about politics all the time. It's good to take a couple of weeks of sometimes; afterwards I tend to jump back in with renewed energy.
2) I was (still am?) in a similar dilemma recently. First, do I have to have an opinion on everything? There are things I know about, and others I know little about. When I look around, there aren't a lot of people who, like me, just listen when I don't have anything to say (yet?) to a given question.
3) Even on a given question, with reasonable background knowledge, there is a multitude of possible conclusions. I can get into all sorts of twistings when I ponder the randomness of that. It's not like mathematics, it is swooshy, subjective, personal, moody, cultural, subliminal... How does our mind work, what are we influenced by... This can drive a man into neuroscience or psychotherapy
4) Remind yourself that politics is a living thing. First, there are so many morons it's unbelievable. My pet theory is that 90% of any given group lacks any kind of intellectual skills. (Mind you, depending on the observer, I'm probably in that 90% most of the time...) But more importantly, we do not have full information. We never will, but, if you're considering World War II, or the Big Depression, you have a lot more information, and you have the development of events that sprang forth since then. You have more context, and a sense of objectivity.
5) Basically though, I interpret your questions in the following way: Politics is a game. Politicians are in it for a multitude of reasons, not the least of which are fame, power, money. The results are those you have mentioned.
Now: Is that a good thing? A bad thing? Can it be changed? I'm not sure. It is a natural, evolving system after all, and it has its merits.
I agree with lurkette: I love this thread. I love the openness of your questions.