To make it to the postseason, MLB and teams, including the Chicago Cubs, need to have a combination of quality players, great performance and good health throughout 162 games. That much comes as no surprise to anyone. To make it to the World Series, you need to do the things mentioned above and get a little lucky once you punch your ticket to the dance in October. Given what happened in 2015, 2016, and 2017, the Cubs have a pretty good understanding of each piece of that equation.
However, since losing to the Dodgers in the 2017 NLCS, the Cubs have failed to win a postseason game and have been unable even to get themselves to a postseason series.