I am not saying that ADCs are supposed to one-shot minion waves and burst down squishies faster than an assassin. Let's get that out of the way.
I would like to point out an issue, and that is that ADCs cannot reach lategame, and as a result, must deal very little damage. This opens up problems in a slightly humorous, but also very infuriating manner.
Let's take a look at where I got my information, then let's go through the process of what a "bot lane carry" is.
Traditional ADCs and APCs are meant to be sustained damage-dealers that are capable of "carrying" a team through battle. In other words, they are like a fragile glass cannon. Certainly, some have defences, but typically, they have very few, like assassins. What differentiates the two is the amount of damage they do in a given period of time. Assassins do a lot in a little, ADCs or APCs do a lot MORE in a lot. Both can be "carries", and for this argument, I will only be looking at Traditional ADCs/APCs, or at least champions that can fulfill that role even though they are not supposed to.
Keeping this in mind, let's look at "sustained damage dealers" in the same category as Caitlyn, and omit troll arguments like Quinn. Just because she's a marksman doesn't mean she isn't an assassin.
Simply because a champion "deals sustained damage" and is "better than my main" does not automatically make me angry. In fact, I like how bot lane is being diversified outside of 16 rotating champions over and over. However, there are some thorns in my side.
Let's look at champions that are meant for a role other than "sustained damage dealers", but are somehow still able to fulfill that role, while doing it better than Caitlyn, who is meant for that role, IN ADDITION to bringing something else to the table.
Let's begin by looking at Caitlyn herself.
Caitlyn has a winrate of 44.64% and a play rate of 2.64%. Caitlyn, a supposed "bot lane carry", sits below:
Vladmir (everyone knows this, and I'm not very mad about it. His winrate is 48% rn.)
Morgana, who is a support geared champion.
Irelia. Do not even try to tell me Irelia is similar to Yasuo, because she is not. She is a battle disruptor who can deal damage, and not a carry. She lives and breaths "Versatility" and not "Damage". Or at least she's supposed to.
Malzahar, but I guess he is sort of in his own category now. He's literally a wave clear machine + ult button.
Kennen is a burst champion, but also deals sustained damage.
Lux, who, ESPECIALLY with the recent patches, is definitely supposed to be either support oriented, or full on burst. However, with low cooldowns, she is able to become a sustained damage dealer WHILE bursting down backlines.
Ryze, who is a waveclear + burst damage + ult mage, yet is still able to deal sustained damage through his low cooldowns.
Caitlyn's winrate is below all of these champions. In fact, out of all of the "significant" picks in bot lane, she sits at the absolute bottom. Yes, below Varus.
First of all, do not bring up the "diversity" argument. I am talking about champions that straight up outclass Caitlyn at what she does, IN ADDITION to doing other things better than her. This is not just "buff caitlyn plz i wanna get a 90% winrate on my main" rant, this is a "Look! That champion deals more damage than your main AND gives a lot more CC/ Has way more mobility / Survives way better/ etc./ all of the above" rant.
"Butbut wait! You forgot about playrate. Get destroyed, get out, your argument is invalid."
Let's look at Caitlyn's playrate: 2.64%.
I'll remove champions with a playrate below 1%, because below that, it's usually more of a counterpick scenario. I think.
When done, these four champions remain. I will think of these as the "Problamatic Four", until someone can explain to me, with sound reasoning, why their presence in bot lane is healthy.
Vladmir: 7%. SEVEN. PERCENT.
Ryze: 1.67% (Out of all the champions, this would probably be the easiest to sway my mind on.)
As you can see, the problem still exists. Why is Morgana sitting above Caitlyn in play rate, and in win rate, when she is supposed to be a support? Why is Irelia, a battle disruptor, sitting above Caitlyn? Why is Ryze, geared towards solo play, sitting above Caitlyn, who lives and breaths ~~"be my slave and give me kills"~~ "Be my teammate and help me set up my traps?" WHY IS VLADIMIR, EVEN AFTER THE NERFS, STILL BETTER THAN CAITLYN, AND PLAYED A HELL OF A LOT MORE?
If you account for the champions below 1%, there is not a single one that falls below 0.5%, although that may be OP.GG's algorithim for considering which champions can be put as a lane champion. This in itself
Additional notes: While Swain technically fits the definition of "sustained damage dealer", he definitely should be addressed, sitting at a 53% winrate with an 8% play rate, and was intended as a "duelist" of sorts, meant to be played top and mid lane. However, I am fine with him being played bot-lane, just not at the rate he's being played at now.
Heimerdinger fits the definition of "sustained damage dealer" through his Q, but also doesn't, through his W, E, and situational usage of his Ult. He's meant to be a little more versatile than a typical "marksman ADC", but also usually requires more setup. However, being honest, his W usually does about two auto-attacks worth of damage, so he should be fine where he is.
Do not tell me that Jhin, Miss Fortune, and Quinn are "Sustained damage dealers." Jhin blows up squishies, just like Miss Fortune, and really only bring sustained damage through their Ults. Do not tell me Quinn is sustained damage. In fact, if you think that is true, read her kit.
Yasuo was meant to be a sustained damage dealer, and is usually played as such. It's just, his sustained damage is very big. That's all.
While Brand is certainly bursty, he's also capable of turning teamfights around with his passive. In this sense, I feel like he deals sustained damage to both the front and back line, but he was designed to do so, and so I'm not mad at him being played bot, but rather his power when played bot.
Caitlyn's damage, and most other "typical" ADC's damage, have been lowered to the point where other types of champions that were initially meant for other roles are now able to fulfill the role of a sustained damage dealer carry better than champions that are supposed to be sustained damage dealers, while also being able to do other things simultaneously. This is an issue, because it creates gaps of several champions shoved out of the meta simply because there are better options in doing a specific task while also able to do more than that task.
To sum up the problem right now, I have an analogy.
If you could buy one super tasty sandwich for a dollar or two, slightly worse, but still tasty, sandwiches for a dollar, which one would you buy? It would depend on your aim, right? If you want to fill your hunger, and be practical, you would buy two sandwiches. They still taste fine, and you're able to fill your hunger up. Much like that, if you want to win by playing a sustained damage carry, play someone who can deal damage AND something else, like Morgana. Deal Damage, CC, and sacrifice none of the range! Otherwise, if you're looking for taste, you would pay for the sandwich that was tasty, no matter how much more expensive it is. If you love Caitlyn's kit, playing Caitlyn into a losing game is fine, because the goal isn't to win, it is to play Caitlyn. However, the way sandwiches should be organized in any given establishment, is that most sandwiches are near the same price range. They don't have to be exactly the same, because variance is healthy for any restaurant, but they cannot be wildly out of proportion. In this case, it is the same for any given MOBA. League is like a restaurant, but with really shitty sandwiches on the menu, really good sandwiches on the menu, and salads that shouldn't be sandwiches but are instead eaten like sandwiches. Burgers can be eaten as sandwiches. Salads are too far. Swain works as a sustained damage dealer in a stretch. Morgana? That's not her goal AT ALL.
Also Address Varus and Xayah because both of them are STRUGGLING!
TL;DR: Why is Caitlyn so neglected? For example: she sits below FREAKING MORGANA in BASICALLY EVERYTHING, when played as the bot lane CARRY. There's an analogy right above that you should read.