Refusing to upgrade the bench turned out to be a major issue
While the starting lineup is as stacked as they come, the Phillies' bench left a lot to be desired. There wasn't a single bat off the bench an opposing manager was ever going to fear, especially when Brandon Marsh was in the lineup.
Philadelphia spent much of the season with a bench that consisted of players like Garrett Stubbs, Cristian Pache, Edmundo Sosa, Jake Cave, and Josh Harrison. That, obviously, is not good enough. There's no bat there that any pitcher would sweat facing.
The depth of this team was tested very quickly when Rhys Hoskins went down with injury. This forced the likes of Darrick Hall, Kody Clemens, and even Jake Cave to play much of the first base before Bryce Harper was well enough to play the field. That was a problem as well.
The season ended with Jake Cave coming off the bench to pinch hit for Cristian Pache, who had pinch hit earlier for Johan Rojas. Obviously, it's not the only reason they lost and there's no way we could know how things would've gone had they acquired a legitimate bench bat, but adding more depth and making this team deeper should've been a priority for Dave Dombrowski.