The other two card types provide other ways to affect the game
As long as shes exerted (which, with her lore value of two, will be a lot), any of your opponents challenging characters will have their strength reduced by three
In Magic there are lots of cards and lots of decks and therefore many things you need to be able to handle, the larger the format the more this is the case
Seven mana is a big ask, but in combination with Sun Titan, Karmic Guide, Burnished Hart, Solemn Simulacrum and Fetchlands, you can recur your whole board constantly
The 'Let Your Power Shine' ability also lets you draw a card whenever you remove one or more damage from one of your characters
I wouldnt expect this to come up super-often, but its a pretty good way to push back against a Control Magic and I can imagine a few other situations where this would come up