One more thing about the value of the bullpen versus the value of a hitter. Over the course of 162 games, a hitter is going to have more value. I'd argue that in the playoffs, a reliever is just as valuable and the bullpen as a whole is more valuable. Why?
In the playoffs the bullpen is going to throw every pitch from at least the 6th inning on, often more. A hitter will see 15 maybe 20 pitches the whole game. Only aces such as Burnes and Woodruff will be allowed to go through the lineup a 3rd time; 3rd/4th starters rarely will. When hitters see a pitcher for the third time they have the advantage of seeing the pitcher multiple times and the pitcher getting tired. In the playoffs there are far fewer instances of a starter facing a tired pitcher for a third time and many more instances of a hitter facing a fresh pitcher for the first time. A strong, deep bullpen creates an advantage that is seen much more in the playoffs than the regular season.
Juan Soto has an OPS of 1.112 the third time he faces a starting pitcher in a game. The second time, an .852 OPS. The first time? .728 OPS. Yes, he has a .958 OPS vs. a reliever but that is all relievers (including mop-up bullpen guys he'll never face in the playoffs) and a .958 OPS is better than that 1.112 OPS seeing a starter for the 3rd time. Put another way, Soto has an OPS of .720 in innings 1-3, 1.112 in innings 4-6, and .890 in innings 7-9. A good, deep bullpen neutralizes that 1.112 in innings 4-6.