I've been telling people in this thread all year that the Cubs are an 86-88 win true talent team, and they are playing to that.
The issue is that this roster is far inferior to 2015-2018.
I would argue that St. Louis isn't significantly better this year than 2016-2018. They have a bona fide ace and their bullpen/defense has been improved. The Cubs have gotten worse, and that's why STL should have a comfortable last week of the season. The NL Central is trash, and LAD, ATL, HOU, NYY, MIN, and OAK would have waltzed through the division. (STL or MKE could catch lightning in a bottle in October, but both have inferior rosters to the aforementioned teams).
The Cubs fans who think that they are not making the playoffs because of Joe Maddon, or mentally weak players will be in for a rude awakening when they go 81-81 next year under a different manager.