Realmuto is weak on defense. It doesn't matter if he has a solid offensive WAR if isn't helping pitchers get opposing guys out. For catchers, defensive WAR - or other stats - don't fully take into account that, with poor framing and average at best other defensive attributes, pitchers' pitch counts and WHIPs are going to be higher. That's a hidden cost for a catcher, which is why catchers with mediocre bats but solid defense are more valuable then guys with higher OPS but weak defense.
Good offense from a catcher helps, but bad defense from a catcher kills.
