This is a retarded fight from those grumpy old men talking about THAC0 being "easy." Of course it is easy to you, you lived and breathed it for decades. So did I, but I remember there being a THAC0 chart in the 2e PHB because it was fucking complicated in that each class had a different THAC0 progression AND the fact that, in a game with almost universally applied rules to additive bonuses, armor and swords with positive bonuses made AC and THAC0 both go DOWN.
So when you are in combat that is getting complicated and you are a Druid that is was blessed by your cleric and using a +1 bow with +2 fire arrows attacking a half plate wearing evil fighter that is on a hill above you but the ground is muddy... the problem is that SOME of the bonuses are actually subtracted from numbers in the calculation. That is absolutely a worse system than AC going up, all bonuses being added, penalties being subtracted, and a single number to meet or beat falling out of the equation.