I won’t pretend to be learned (well maybe I’ll pretend but I am not) but your article seemed to be a warning of inevitable circles and a warning but wrapped in a large amount of speculation of what could happen.
But the exact same things won’t happen, the black plague was a product of early global trade bringing back disease from the new world. Epidemics can still happen but we better prepared. The Christian religious wars are unlikely to reoccur in the same way and Europe isn’t in as much danger to threats to royalty as it was a century ago. And we have learned better ways of handling the outcomes of war than those who imposed such conditions on Germany after WWI.

There are tensions in the world at the moment, mostly power struggles in various forms — that hasn’t changed. But many people like you the author are aware of these trends and can info wide audiences of the potential so it we aren’t caught unawares. The two major developments you mentioned Brexit and Trump are still being played out but they are not inevitable. While most people felt them unlikely to move as far as they have they are now the focus of attention much earlier than the rise of the Nazis become a focus.

Mass psychology maybe too hard to influence but there are some factors that are clearer than others mainly inequality from global trade. If that could be addressed many of the obscene hand gestures could be diverted into productive use. Utopia will never exist but fairness will alleviate the worst and stop major movements lead by war mongers and colourful pied pipers. The focus of world trade needs to change from the numbers to the people, when peoples basic needs are met, food, security and a means to create hope for the future then tensions can be reduced.