User blog comment:Aphostropils/Questions from a beginner/@comment-26186030-20160404023909

1. ADC's don't have a bunch of good damage-resistance items because AD champions get a 100% ad ratio ability that can be cast up toi 2.5 times a second and is garunteed to hit, auto-attacking. This means that on most ADC's there aren't built in openings for them to get melted without being able to unload lots of damage on your team. Meanwhile mages deal with cooldowns that often go over 10 seconds for a spell that isn't garunteed to hit, leaving them vulnerable during the 10 seconds they can't use that ability, especially if they miss it. Mages get to have Zhonya's and Abyssal to cover up their weak time inbetween spells, a weakness that ADC's don't have.

2. Meta is what's popular, and things become popular for a variety of reasons. The most common reason for something to become meta/popular is having someone use it in LCS. No one used ZZrot portal before we saw it in the LCS (excluding that banner cheese in URF) because no one knew about it. The other way for something to become meta is for it to counter something popular, i.e. Lee Sin jg into the Mundos and Jaxes that have been seeing play more often since the season started.

3. It'd be broken for a Marksman to also be useable as a tank or support because of the utility that such a champion would have. ADC's are balanced around having damage in exchange for utility, and Tanks are balanced around having utility in exchange for damage. Having insane utility/inherent tankyness on a champion that builds full damage is absurd, just think how bad it would be if Draven had Thresh-level utility. I know neither of these extremes are normal on ADC's and tanks, but think about it for a second.

4. It's always better to adapt to what you see in a game than to just build the same items in the same order every game. Having core items is important, but if you don't have even a bit of build versatility you're going to get screwed over several games because each game is different, and you'll need different things for each game. In the same way that certain champions don't work in certain matchups certain items don't work so well in certain circumstances.