Kirk is a far better blocker and framer. Unless you think that framing is somehow not important for some reason that's two key defensive skills where Kirk is far more effective, and Kirk even has really solid throwing metrics this season as well so he's closed the gap in nailing baserunners this season as well. It's a shame that the bat has gone backwards but he's shown improvements in his batted ball metrics that have yet to materialize into more hits, and he's arguably the best overall defender behind the plate as well. I still hope he can regain a bit of offensive output in the future, whether it's this season or in the future with a new coaching staff.