Love that review! Exactly the kind of feedback that spurs us hobby devs on to make more and more games.
You're correct, the level layout in Sky Raider Redux is procedurally generated which means no two games are the same. Only the bosses are identical in terms of frequency and behavior. Also the hitbox on your biplane can't get much smaller! It's already a tiny sprite.
James and I intentionally enabled different play styles for different gamer preferences. You can play for high score, you can play for best level, you can play on one life only and restart from the beginning, or you can continue where you left off. You can even push the boundary and see how far you can get past 21 since there are no saves after that! The game doesn't force you to only play one way.
We also put in a lot of detail on the audio/visual upgrades. Your plane has the spinning prop and the plane banks from left to right. Enemies and obstacles have more of a 3D look compared to the original demo. There is in-game music which alternates, plus a "death jingle" and "boss tune." Even some of the bosses have extra animation like the jet fighters banking left and right, jet exhaust animation, and of course the spinning blades on the helicopter. These small details might seem like simple improvements, but they take more time and effort than you might think and James deserves credit for everything he did to enhance the game. Hopefully Sky Raider Redux really provides a nice experience for the player. I know I certainly enjoyed playtesting all the boss fights!