Cards like Living End, which cost nothing but are hard to cast normally, can take over a game in an instant, but this one-mana instant can stop that with ease
I think the comparisons to Expressive Iteration are a bit of a reach, since Flow State requires two different card types in your graveyard, but if youre in a Constructed or Commander deck that can bin an instant and a sorcery easily, this is some powerful card draw
There are some cool Cube cards here, but nothing that you couldnt skip for most Cubes, while offering unique tools for more niche designs as well.
While the variance can mean whiffing a bit, there are ways and decks capable of doing such things
Its removal is fairly efficient (see Lightning Bolt), but it doesnt scale well into the game as creatures and boards get larger
Key to the City is a good way to draw cards, too, especially if you can tap it and untap it through Artifact shenanigans