Thanks for the well articulated feedback! I think the difficulty for this project was too high as well, and I agree with everything you touched on.
I had the projectiles come rapidly to incentivise players to use the watering can, but looking back it was still too fast.
I tried mitigating the instant deaths from recently spawned projectiles by disabling the colliders for the first few frames, but I don't think it was enough. If I had given myself more time I could have spawned them at a much lower scale and sized them up before adding velocity.
Remembering the bosses pattern is one of goals I wanted players to learn. Though, I definitely became blind to the difficulty as I made and playtested this jam much longer than any player is expected to.