Yup. There's a difference between throwing s*** at the wall (Bailey/Hanrahan/Melancon/et al) that we've seen in the past and valuing the right players. If they wanted to overpay for Kimbrel and two other versatile arms in the pen, I would be hesitant to say it was a bad call.
However, as bullpens get more expensive, the Sox will have to maximize value elsewhere.