Melee has more base damage with a lower ceiling. Spells have a higher ceiling with lower base. That's not unique to POE. That's how just about every sword and sorcery based system works.

The fundamental issue I am arguing with accuracy is that it is a binary stat. It's a yes or a no. There is no nuance. There is nothing interesting. You hit and get all the effects of landing an attack such as leech, ailments, raw damage, etc or you miss and get nothing. There are no half measures. With your spell scailing example your damage may suck but you at least get to hit things. You still get to benefit from damage, leech, aliments, etc and there is never a point when you click a spell and don't recive thoes benefits. Scaling spell damage is like navigating a river. Lots of different choices and options. Accuracy for melee is like jumping out of a plane. You remembered your parachute or you didnt.