2 WAR for a season, often viewed as a baseline for an "average" full-time regular, seriously undersells any catcher who achieves it.
First, the number of starts behind the plate serves as a limit on the plate appearances. It's just harder to accumulate 2 WAR of value at the plate when you're playing, say, 2/3 as much as a good starting center fielder or shortstop.
Second, if the catcher is a good enough hitter that you want him in the batting order even on his "days off" behind the plate, the versions of WAR I'm familiar with apply a penalty for the games as a DH. While there is a defensive bonus for playing catcher, a lot of it is negated when you DH. (This is true of hitters like Byron Buxton as well.) The DH penalty is well-intentioned, since the bar is very high to be a positive contributor there. But still, trying to be even a 2 WAR player is very hard when DHing very much.
A catching tandem that together earns 2 WAR is arguably major-league average. One catcher doing that by himself is considerably better, as he leaves room for his backup to contribute too (if he is capable).