Yes, measurements can definitely tell how close to "neutral" a device is. Another term for neutral is
audibly transparent. But you need all the data, not just frequency response. There are also several types of distortion, ringing and, for electronic gear, noise and time-based problems like wow and flutter. My
Audiophoolery article explains a lot about this.
I'll also mention that audibly transparent is not boring and lifeless as is often claimed. Harmon has done extensive research using loudspeakers, and they found that people universally prefer speakers that are most accurate. Hey, don't you want to hear exactly what the mix engineer and producer heard as they honed the music?
--Ethan