You can luck into a good bullpen, but you can't count on that. Things have changed a lot in the last several years. I have been an ardent baseball fan my whole life, but paid little attention in the late teens. Fans always compared pitchers by ERA and WHIP and to a lesser extent K/9 and K/BB ratio. ERA and WHIP can be influenced by team defense and positioning. How many outs have been lost by bad outfield breaks or shifts being beaten and how many hits and runs have been saved by good defense and positioning. Tepera and Loup were great signings if you look at ERA and WHIP. Iglesias has lost 2-3 MPH on his fastball and sinker. Why? I don't know. It's the job of pitching coach to figure out why. Wise needs to compare good Iglesias and bad Iglesias. Is there a difference in arm angle or stride that makes a difference?
I think every pitcher needs to be evaluated, not just by ERA and WHIP, but by velocity, spin rate, drop and the differences in all these within their pitching arsenal. Also, there has to be stats available for the the percentage of time the strikes are in central 2/3 of the zone, 80%, 90% etc and the ability to hit the corners. There is enough data out there to make more informed decisions. They just need the time and intelligence to use them.