You make a very good point with the dashing that I didnt think about. None of the enemies before the boss encourage you to dash, so it makes sense that suddenly requiring you to use it in the boss fight is unintuitive. In the future, I will try to (re)design enemies more with the dash in mind.
About the boss's difficulty: For me the fun of games like these is that you fail often, retry, learn and become better over time. It makes finally winning feel more rewarding. Therefore the boss being difficult is intentional, I don't want people to generally beat it in the first few tries. I hope that doesn't discourage you from playing :)