Why 100 years? I'd say we haven't fixed those in 10000 years and will never fix them, unless some divine intervention changes human nature.
> Why nobody is working on a replacement society and economics system?
People are working on it, but the last time revolutionaries got into power on a large scale, 60 million of us were killed or starved. People became quite cautious of revolutions after that. But don't worry, the memory has almost faded and a new generation is waiting in the wings, ready to bring about utopia through mass murder.
People talk about it all the time. Everything gets blamed on capitalism these days. Problem is nobody is offering good alternatives. Good luck finding one.
You can find alternatives, but no politician wants to run experiments proving or disapproving them. They'd rather argue them instead. Why not follow the scientific method and run a small experiment on a subsection of a country to see how it pans out? Why not collect the data, review it, and try again if there's enough variables? The reason I suspect we don't see this thinking is (1) politicians, at least in the US, are predominantly wealthy Ivy League Lawyers trained to "solve" problems through arguing - they are not scientists trained to run experiments, and (2) in every political system the folks who rise to power are those who benefit from the current system and therefore have no reason to risk changing it.