In terms of power, this new mechanic technically sits between its predecessors, but the mechanics strength is rarely the deciding factor
Saga creatures: You can summon monsters in certain Final Fantasy games, and MTG recreates this with Saga cards
Sure, each half costs one mana more than the split half, but you can add in interaction in your creature spots or a creature in your interaction slot and then a beater later to close out the game, and you can get both effects for one card
Not only does Lumiere give your characters an edge in combat, but it also protects them from Sisu Empowered Sibling
You can tell a lot of care went into the design of the deck, and that's just one of four Commander precons, let alone everything that'll appear in the main set