Building a quality bench is more difficult than it seems. Bench players are like relievers. Their performance can fluctuate wildly from year to year because they inherently work in small sample sizes, and weird stuff happens in small samples. A bench guy will hit .330 with a ton of clutch hits one year, then struggle to get off the interstate the next. Happens all the time. That’s baseball.
The Yankees have spent the last few years building their bench through trades and from within. Signing free agent bench players is tough. Bench guys usually look for the most playing time when they hit free agency, and the Yankees rarely offer that.