Oh, Carbuncle - at least you try your best.
Final Fantasy is no stranger to status effect-based Summons, and there are plenty of examples that help to heal the party. Even so, these Summons tend to be a bit more situational than most - most players will have at least one character
in their party that’s focused on keeping the team healthy, so dedicating a Summon to the exact same role doesn’t always make sense.
That goes doubly for Carbuncle: in most of its incarnations, Carbuncle casts a spell called Reflect. It’s a halfway decent spell, especially when going up against certain bosses... but in most Final Fantasy games, Reflect is a low-level, easy-to-find spell that doesn’t cost much in the way of MP. Simply put, Carbuncle is mostly a costly, inefficient way to use a spell that most players will find early on anyway.
Really, Carbuncle’s only redeeming feature is that it’s basically a cute little cat-monster, but that doesn’t make it any more useful in the middle of a fight. Pro tip: it’s best to save your MP for just about any of the other Summons on this list.