Thank you for your detailed comment.
Overall - the main goal for this prototype has been to create a solid gameplay/mechanical foundation, and focus wholeheartedly on the audiovisual presentation. I'm happy to hear that you enjoyed the aesthetics and the music. Your complaints about gameplay are perfectly understandable coming from (who I assume to be) a seasoned shmup player - however, I believe most of your criticism comes down to expectations.
Every enemy wave is a sort of positional mini-puzzle. The "lack of decision-making" may be applicable to the absence of the strategic elements like bomb, hyper, rank and other kinds of management, but the tactical considerations are definitely present. You are forced to react to each new wave and decide on the spot - Where do you move? Which enemy do you shoot first? Which enemy do you switch to after killing the former? Some waves are trivial in this regard and literally never shoot you, but others may pose significant threat if "solved" incorrectly. Purple and Fish subvert this dynamic heavily, but with Yellow it is the primary intention, especially in Hard mode.
Sounds to me that you've played advanced shmups so much that those tactical situations have become trivial to you, being able to engage threats optimally on the fly. This is fair, and I can certainly relate. However, from my experience making games, talking to devs and observing the scene, very few players actually possess such sensibilities. Judging by how the other commenters note the game's simplicity without outright saying it's a flaw - I think it's a valid reasoning that most people are satisfied with the amount of decision making currently present. I guess we'll see once there are more comments.
That said, the game is really meant to be a foundation to be built upon. I had a lot of ideas that couldn't make the cut due to time trouble. For example, the way in which our game implements the theme - Core Stability (which you managed to completely avoid interacting with through no fault of your own, oopsie) - is rather limited at the moment, mostly affecting the audiovisual aspect and not so much the gameplay. It's also made completely irrelevant if the player never ever dies. Which, to be fair, mostly people that aren't you or me would die at least a few times on Hard, which will force them to interact with it, so I consider it a decent implementation.
I appreciate the music idea. Music-synced bullet hell is something I've already done before, but for this jam I wanted to avoid scopecreep. Synchronizing Reverie Breaker to the music would result in a completely different game, so this is unlikely to happen save for a TLB or something. Either way, I'm glad you could still enjoy certain aspects of the game.