5, 4, 6, 8, 5, 1, 6, 2. 4.63 runs/game
That is how many runs the Cubs have given up in their losses. You can at best blame the offense for 2 of those.
10, 5, 0, 2, 0, 6, 4 3.85 runs/game
That is how many runs the Cubs have given up in their wins. The offense should get credit for 4 of those wins.
Let this sink in the Cubs have allowed 3 runs or less in 4 games all year. The have scored 4 runs or more in 8 times. If the pitching was better the Cubs record would be better. If the offense was as bad as you think it is the Cubs record would be much, much worse.