The trees have no hit box. Zombies have no hit box when they rise. Mermen have no hit box when they attack.
Axe knights throw indestructible axes like I already said. But at least you can duck to avoid the top axe. In practice you should be able to jump the bottom axe. But good luck doing that.
The ladder snakes shoot indestructible fireballs that track your position so they're even more annoying.
The bone snake boss and harpies are the worst at this. Because they shoot multiple projectiles in a cone shape and you have no choice but to take damage.
I understand they probably wanted to make the game a little more difficult but that's not the way to do it. I would gladly take back death pits and fixed jump arcs if they would fix the projectiles
Mermen can definitely be hit while they're shooting, i don't know how you assumed otherwise. As for the Snake Ladders fireball, it's not tracking, and the three way projectiles are as usual meant to be dodged from a distance, of course standing too close will result in a hit. About the lower axe, why you don't consider jumping an option or difficult to pull off? That's literally what you are meant to do and you can even change direction mid-air. I don't get your complains at all, you genuinely got me confused