You do know that Fowler is hitting .227/.328/.418 this year, right? That’s an OPS+ of 98. Fowler has been a below average hitter so far this year, and has only had 14 PA over the last 10 days. His WAR for the season is only 0.2, and Almora’s WAR is 0.4.
I agree that lots of stuff isn’t going the Cubs way so far this year (not surprising that a World Series winner will regress the following year), but I think it’s pretty hard to pin it on the loss of Fowler.