Thank you for the feedback. The collision box for the dragon is quite a bit smaller than the sprite. The pillars also have a smaller collider. I think the problem is I switch to the end screen instead of showing something like a death animation, as that would more clearly show how forgiving the colliders are.
The trick is to mix up dashes with flaps. If you notice that a flap will cause you to hit the upper pillar, you can quickly dash, and that acts as a flap cancel.
But I do agree the game can be very difficult. And unfortunately the way inputs work are one of the reason. One thing on my list was to do input buffering, similar to how quality platformers like Hollow Knight and Ori do it. If you press a flap while you're dashing, it won't register. I also think flaps could act as dash cancels, giving you even more control over the dragon.