I actually agree with almost everything you said. I put a lot of thought into the learning curve because I think it's something many people don't pay much attention to in game jams since the games are usually short.
I also think I could have handled the cooldown much better. I implemented it that way at the beginning, and it just stayed like that. The dash is the core mechanic of the game, though, so I spent a lot of time making sure it felt good to use.
As for the items, I'm not very proud of them, to be honest. They definitely could have been designed better, but it was a short jam, and I had to come up with them quickly so I wouldn't spend too much time on that part.
I really appreciate your feedback. Comments like yours are exactly why I want to keep improving the game even after the jam. Thank you very much! :D