Champions have strenths and weakness and things that stop them from doing what they want.

I get told alot of the time marksmen are early to mid game champions but does any one see that when late game comes marksmen and crit carries have items and masteries just with aiming for damage and crit that give them healing, mana healing, damage, damage amplification, MR, hp, mana, cdr, attack speed and movement speed. only thing crit carries dont get in their build path is armor and ap now. only ap casters got all these things available for them in the design before but ap casters dont constantly stream out damage they they do it in bursts (well except for assassins who burst and and burst again and burst again so its less burst just constant high damage) and didnt get everything on basic autoattacks.