Ah, History! I was generally good at it in school, but managed to fail my O Level (though I got the usually essential 5 passes, inc English & Maths). I blamed the question-setters. However, the syllabus and standards of teaching varied widely round the country, and I suspect little has changed?! We seemed to cover the Romans, Henry 8th and Wellington/Napoleon almost endlessly, but by subsequent watching of many documentaries, I've filled-in many of the gaps, especially re North America, WW1 & WW2.
For the OP, and others, blaming our bloodthirsty past, well, yes, sadly Mankind is like that. As recently as the 80s, the Rwandan tribal conflict massacred between 1 and 2 million innocent victims, just after WW2 India had to be partitioned due to the massive religious bloodshed there, and even in the 90s in civilised Europe, there was a genocidal conflict with innocent civilians being massacred in the Balkans. Oh, and I nearly forgot the massive loss of life in WW1 and 2, and that driven by Stalin and Mao.
We can only hope that 'civilisation' finds a better way forward, maybe at some point the UN (an org unthinkable in its concept for most of history) will work out how to stop the major powers using their Veto to block resolutions if THEIR interests are affected? And recognising historical mistakes is all part of that, isn't it?