Hard agree with Pat on this one. Except that I didn't really like it even in Final Fantasy Tactics, either.
I love the idea of being able to customize and mix-and-match powers/skills/abilities and all that, but in actual practice, it tends to be one of the main things that leads to me entirely abandoning a game <25-50% into it, especially in the games where it is apparently required to do it perfectly "optimally" or else you're gonna have a bad time (or, worse, the game becomes literally unfinishable.)
Haven't played Backpack Hero at all, and it doesn't look like something I'd care about. I mean, right there in the three visible tags is yet another asinine permutation of that term that I've grown to hate so much. "Roguelike Deckbuilder." It's like, yes, these are English words, sure, but when those English words are used in that particular configuration, they mean next to nothing to me. Or, rather, "Don't waste your time with this game," is what they mean to me.