Most people wonder why so much bad stuff happens. Why did we, the Blue-Haired People, declare war on the Green-Haired People? It’s because we’re violent people, (so one line of thinking goes), and so we attacked our neighbors. Why is our economy in such a mess? Because we’re greedy people, and we stole each others’ pensions. Why do so many have health problems? Because we’re lazy people, and we don’t exercise enough.
This type of thinking is a variant of the fundamental attribution error – assigning blame to people’s inherent nature, rather than circumstances. In this case, you blame collective nature instead of individual nature. Of course, sometimes, nature really is to blame… but that’s far less common than people usually suppose.
A quick check against this sort of error is looking at history. Human genetics haven’t changed much in the last thousand years. Hence, if some problem is inherent to human nature, it should be present in every culture and every time period, from New York City to Timbuktu. Is that really true? Usually not.
To take a simple example, the Roman and Carolingian and German nobility had all the food they could want, and no obligation to work. (Indeed, they often dressed impractically, to show they didn’t have to work.) Were they all obese? No. Some were, certainly, but it doesn’t seem to have been regarded as a society-wide problem, like obesity is now. Hence, whatever the cause of obesity, it can’t just be “people should eat less”, or “people should exercise more”. If that were true, people would all get obese whenever there was enough food and no manual labor.
But what if a problem really is inherent to human nature? For example, humans are usually somewhat selfish, in the sense of valuing their own welfare above everyone else’s, and that seems pretty universal. But if that’s the case, there’s no point in complaining about it – we should just give up, and look for another angle to attack the problem from. If something is set into the human genetic code, and it’s present in all cultures and time periods, saying that it’s bad is no more useful than cursing gravity for dishes breaking. For a plan to be valuable, it has to be one we might actually implement.
The Rationalist Conspiracy 
Are we allowed to complain about Death?
I agree that it’s not worth complaining about something without a plan of action to fix it, but it may well be worth a lengthy, uncertain, generations-spanning quest to solve the problem.
Why on earth shouldn’t we blame humans?
Humans are pretty terrible.
Not every belief has to be a plan for action.
Not every belief has to be a plan for action, but blame isn’t just a belief, it’s a moral judgment. The purpose of blame (insofar as it has one) is to optimize the world by creating disincentives to do damaging things. The human genetic code doesn’t respond to incentives; hence, blaming it like you would blame an individual human is silly.