Polarization between parties has fallen in world democracies, with only a few outliers ( looking at you America).
A paper by Stanford University looked at questions from the American national election studies, surveys were given to supporters of various parties, and asked to rate themselves using a political thermometer 0-100. In 1978 Americans scored 27 degrees colder towards their rival political voters. In 2016 the coldness widened to 46 degrees.
For the UK, Brexit had little effect on polarization. The divisions on the EU crossed political lines. The study was also not useful in Germany as only the more affluent West Germans were surveyed.
One explanation for the widening is Public Service television budgets. Countries with the least budget have highly partisan news networks (FOX NEWS, CNN).