Three problems sit underneath every other problem humanity has, and they are largely invisible at first glance.
The biological problem is that our behavior is strongly shaped by our genes. Twin studies in behavioural genetics put the heritability of most behavioral traits near half, and evolutionary psychology has been showing why for decades, though society is still catching up. Understanding this makes it easier to accept ourselves and others, and unreasonable to expect people to change their minds easily; some brains are wired like a program that returns one result. We also carry a built-in list of cognitive biases, the most influential being confirmation bias, which I treat as the ultimate bias, and the deeper constraint I call the reflexivity limitation. Progress is still possible, only slow.
The social problem is the set of imperfect institutions that grow out of those biological limits. Edward O. Wilson put it best in a debate recorded on Wikiquote: “we have paleolithic emotions; medieval institutions; and god-like technology.” Technology, at least, is a positive outgrowth of our biology, and history shows the social problem yields: advanced nations have built relatively stable societies, a long way from the “solitary, poor, nasty, brutish, and short” default that Thomas Hobbes described.
The entropy problem is the least acknowledged. Its formal statement, the second law of thermodynamics, sounds abstract, so I prefer the mnemonic from Steven Pinker: things fall apart. Bodies, societies, and the planet decay without attention and upkeep, and life is a constant struggle for survival and flourishing.
Whether the pace of progress is limited to the gradual change we have seen, or whether solutions can be accelerated, is the essential question for our species.