In what I've identified as the MacPhail-Ryan era (1986-2015), the Twins have consistently emphasized offense from their catchers.
That is not to claim that they've had poor defensive catchers throughout that period. Joe Mauer, for 10 years, was not only one of the the game's most productive hitters, he was a superb defensive catcher as well. But the Mauers of the world are rare birds; most teams in most years have to decide which set of skills to emphasize at catcher and which set of weaknesses to live with.
Tim Laudner and Brian Harper, the regular backstops on the two World Series champs overseen by Andy MacPhail, were not particularly well-regarded catchers. But Laudner had power, and Harper was as good a contact hitter as could be found, regardless of position. A.J. Pierzynski, who preceded Mauer as the No. 1 catcher, was a better hitter than receiver. Ryan Doumit was a bat who caught. Mike Redmond's appeal was more in his bat than in his defense. The Twins spent a couple of years trying to convince themselves that they could live with Josmil Pinto behind the plate and only gave up on him after a concussion-riddled 2015.
They did have some glove-first catchers during that era -- Drew Butera, Henry Blanco, Tom Prince -- but they were intended to be backups to catchers who were good hitters.
Castro is not Butera-weak as a hitter. He has some power, with double-digit homers in each of the past four years. But how well that power will play in Target Field as opposed to the cozier Houston yard is a question; he's hit almost twice as many homers in his career in Houston as on the road in almost equal playing time.
But that's about hitting. The new regime is putting a new emphasis on catching defense. As one who has preached for a long while that the easiest way to improve the pitching is to improve the defense, I certainly can't argue against that philosophic change. And as one who wanted to see the Twins increase their use of analytics, I certainly can't argue against the process that led them to pursue Castro.