But personally I feel like the movement and animations are way too sluggish and not having a way to aim up or diagonally makes the flying enemies more frustrating than feels necessary.
Please remember this is a demo before we've truly started development of the game, so certain features won't make it in due to technical complexity, or won't be as polished as they will be in the final product. The lack of up or diagonal shots is one of these, shooting horizontally is relatively easy to implement, but especially diagonals are actually really difficult to implement.