The reason why ADC sucks and possible solutions
I am a diamond + support main but i am also able to play every role in above diamond level. My peaked was at diamond1 20 points in one of the season and i have played all season from 1-6. I have dota 1 background and very skilled in it as well. Although I am not challenger I am decently skilled in terms of the LoL ranking population so what i say have some credibility and it is not out of my ass.
http://www.lolking.net/summoner/na/569239
Random Trivia: I want to say something that might sounds crazy but ADC actually scales reversely. ADCs/Range AD like jayce are overpowered level 1 in other lanes. If you play melees top vs ranged top then you will know exactly what i mean. As a melee have to give up some CS due to free harass then you will get shoved in and get harassed for free under tower when you CS. As for mid you can't trade well early b/c your spells does no damage at 1 level and in extended trade you lose. Basically to beat ADC in both Top and Mid you have to wait for your power spike then burst the ADC in a short time frame and disengage or kill. So yes ADCs are OP level 1 but i can’t deny the fact they fall a cliff later in the game.
Problem 1: Keystones Damage Creep Keystone is the worst thing happened to this game. It made the game damage creeped so ridiculously high. I can't even believe it staying for another season and the CotC mastery made tanks harder to deal with when you only have 1-2 items as ADC. To put it into perspective lets compare TLD VS Havoc ( +3% damage). Lets say an AP mid laner @ level 18 has 600 AP so his TLD will deal 240 damage. So what this basically means is Havoc requires you to do 8000 damage in your spell rotation to deal 240 extra damage. This proves how much damage creep TLD did compared to the older seasons masteries and the other damage keystones are as busted. This directly affects ADC’s possibility to survive in a fight because they will build no defense in order to do meaningful damage. The game's masteries system was balanced for 5 season based on the numbers on the older masteries. So If you decide to add so much damage creep into the game then you have to have way to negate the damage creep within the masteries system. Well, might as well not have it to begin with.
Problem 2: Other laners and junglers dictates Bot Lane laning phase time Other roles decides when you have to end laning phase and start rotating to take other towers or match the rotation to prevent another tower lost. So ADC are forced to not farm as much due to pressure and the current game flow. Gold will not funnel into you only because this is not DoTA and everyone is a carry. I think the issue is mostly coming from junglers. The better jungler will always come DK bot lane @ lvl 6, take tower, take dragon then the game snowballs and accelerates the game flow out of control. Junglers also make top have a hard time as well due to the fact Top and Bot are dangerous lanes due to the length of the lanes. The best way to fix this issue is nerfing their experience in the jungle while keeping their gold the same. The best way to determine the amount of experience nerf is to match the Jungle level to the Bot lane. There is no reason why Junglers should be 1 or 2 level higher than bot lane. Junglers should only exist to maximize the gold/experience in the map and not to oppress enemy laners in an unhealthy manner. In a perfect scenario if a full level 6 2 VS 3 with an enemy jungler occurs then it allows a possibility for the 2 Bot to out play the 3 with their ultis thus allowing counter play.
Problem 3: Riot thinks ADC are carries when everyone can carry. Other Classes requires less gold to be effective. Say if Irelia gets Triforce and you just finished IE or ER there is no way you can 1v1 her. Hell even zyra with Eye of the Watcher and sorc boots can 1v1 you. I dont think there is an point in the game where you can fight 1v1 anyone in the current meta. In team fight you don't do damage to a tanks till you have finished a BF item, Zeal item and LW item. Or AP just shoots you with 800+ range spells while you only have around 550 range. Or you get jumped by the bruisers and get one shoted. ADC requires too much gold to anything meaningful and it doesn't feel rewarding to play. And it kind of ties in with my point these enemies have crazy amount of damage from keystone masteries and you are forced to rotate so you are getting less gold compared to an traditional extended laning phase. I think lowering the cost of all the BF items is a good start.