There are other C in the pipeline, but none anywhere near as good as Realmuto. He is throwing out 45% of runners this year, easily leading the league, His defense is elite and has been most of his career. (although this rate of getting runners is oddly high for him, but new team, new pitchers)
The entire team is underperforming on offense, at some point this is going to fall on the coaching. Every player is having a bad year except Kingery, and he is fading pretty fast to what I suspect is more normal numbers.