Honestly: Marksmen need ammo systems. All of them.
I'm legit tired of seeing people getting mad over marksmen. The role isn't that easy. It's super stressful with a target on your back, being super-dependent on hoping that your team realizes they need your ass to win the game, and on top of all of this, your support could just be one of those e-girl types that just want to get carried instead of actually be good.
However, marksmen LEGIT DON'T have good counter-play options for their power curves to feel fair to every other class. Once again, I'm cutting the bullshit and most of the sarcastic filler to explain my reasoning.
We've reached a point in League of Legends when it comes to counter-play. Good examples of a well designed kit is something like Cass, or Maokai, or Nami (yes, every time). They have a thing they do, things they don't do, time stamps they're strong in, and don't just encompass the entire spectrum of their class on their own.
Enter marksmen, who, as a class, embody none of this line of thought. How do you stop Kog from running your team over? By ending the game before he gets to a point where he's nigh unstoppable. What type of "counter-play" is that? Now, from before this was acceptable, but this is 2017, soon to be 2018. We're gonna need more feasible answers as to what to do with a marksman that's...well...doing shit. We have a possible solution, but I can understand the fear in pushing adcs into it since that's the type of change you can't just "revert" and pretend it didn't happen.
I'm seeing posts about crit...a lot. Crit isn't the problem on its own, though. It's more like crit...with no breathing room for that damage output. Think about it. Almost every other champion in every other class has some form of gate or down time from their dps. Even someone like Cass can't get her full damage out if you aren't poisoned. Vlad was changed to have more delays in damage output and healing (hell, even itemization changed for it). Most champs work in some form of spell rotation, or require spells to be up to really get the ball rolling (Azir, for example). Marksmen? Regardless of what damage they can do, they just DO NOT stop doing it until you die, they get cc'd, or one of both of you leave interaction range. Sure, they're the dps class, but no other form of damage output in this game just...goes like this. It literally doesn't end, nor does it have to, until you die. That's where a lot of the issue lies.
It's the same pattern all over again. Every time we do this, we have like 3 or 4 super op marksmen and the rest are B tier at best. Then Riot eventually addresses most or all of the top tier ones and then we have a new reigning OP until we whine for another mass marksman tuning. It's a cycle that repeats itself, and there isn't enough that defines one marksman's play from another one's to add variety to what lanes they go to (except Lucian and Corki apparently) or what they really do well or don't. When you need an early game marksman, you just pick any of them. When you need a late game marksman, you pick any of them. There's no feeling of real gain or loss from the picks, so long as you kinda "hit the ballpark".
So what would an ammo system do? Basically what it does for champs like Jhin and Graves. By designing unique types of autos and reloading mechanics, it'd better differentiate each marksman, but the important part is that it'd open up windows where marksmen are actually vulnerable, especially late game ones that just pepper your whole team down behind bodies and shields. That way, there's actually something to play around during fights, where assassins/divers can use bulkier team mates to use up the ammo of the enemy marksman before going in while they're reloading or low on ammo. It's way better than them reaming your tank and going for you next, right? It'd also even the playing field between the delayed burst of assassins and the newly limited sustain damage of marksmen if this were to happen.
I'm a guy that prefers the health of the whole game above all else. If I see a problem...like a real problem, I post on it. Adcs are a real problem, and they need a real solution so they aren't such an issue to the game's balance as a whole.