False. You either are a new player - started last season or sooner, or you aren't reading carefully - no offense meant. Let me explain more clearly.
In seasons past, adc's that positioned too close behind their frontline could be initiated on by a good flash or dash from someone like renekton, malphite, vi, etc. This would be followed up on by someone like another bruiser or fighter OR by a mage or assassin. In such an engage, the adc would GUARANTEED die (or have ga popped) for positioning poorly. This rewarded the other team PROPERLY for engaging well. Currently, it's more like a 50/50 of it the adc would die in such a scenario.
To avoid this, adc's AND squishy mages and assassins would have to position further back until the opposing team had burned their initial hard engage. After this, they were safe to be closer to the frontline and dishing out their burst or dps. This also works in the current meta - as it should; adc's who position properly do not get blown up. No issues with this. Issue is with the fact that even when they fail to do this, they don't die for it when the other team executes properly.
When I say no damage - consider this - I can build 200+ armor on a bruiser, and thanks 4 crit item, ga, lifesteal adc and current setup, I will still take like 900 dmg aa's. Replace the lifesteal or the ga with a last whisper type item and you get up to maybe 1400 on crits. Your attack speed is at least 2.0 - thus 2 aa's per sec. So you are doing 1800dmg per sec to 2800 dmg per sec to a TANKY champ. Through 2 armor items plus ninja tabi, you are doing more damage to an opponent than a burst mage will do with their full combo when the opponent only has ONE magic resist item. You get to keep doing this level of damage for as long as you can aa. Considering most bruisers have maybe 4k hp, you will kill them in... about 2.5-3 sec. WTF. Just think about how obnoxious that shit is for any other role than adc to deal with. Let me help you picture it better. Have you seen a fed well-played yi or xin in a low elo teamfight? That's literally what adc's get to be late game regardless of if they are fed or not just because they are an adc. With their advantages of: range, mobility, 2summoner spells for survival (vs ignite, tp, or smite other roles usually have), peeling from teammates, shields/heals/ults they have more protection than any other role. Furthermore, they currently can get massive healing without even building lifesteal. Almost no other role can take that rune or they will get destroyed in lane for it. With all this, adc's have the proper tools at their disposal to carry if they play well enough to DESERVE to carry. But rather than do this, we make them even stronger or other roles with DAMAGE even weaker so they are FORCED to carry. So other roles are FORCED to be supplemental damage at best.
Let me help you picture this better from a toplaner perspective. Imagine you are an adc and you get fed in laning phase. Despite no help from jg or mid or tp's from top, you overcome multiple ganks by the enemy jungler and mid and win your lane hard. You have a 2 level advantage and half an item lead. But your toplaner fed the opposing darius. If you splitpush the rest of the game, you will be collapsed on by multiple enemies and killed because your team is too weak or too dumb to sit at a tower and stall the other team while you split 2v2 and win the game. If you teamfight, despite your proper kiting, you get run down every fight by the enemy sej cc, or the enemy galio cc, and the lulu buffed and sped up enemy darius. You play as perfectly as humanly possible, but your teammates just don't have the damage or know how to play properly and no matter how well you itemize to kill darius and defend against his damage, he kills you. You either have to spend 98% of the fight zoned away from doing any damage as your teammates get aced and leave you to 1v5 defend inhib tower or you die because you fight as best you can with your team. How fun would such a game be as an adc? How fun was it when that exact scenario could be done to you by not a darius - but a tank doing that much damage to you? It wasn't fun - it was bullshit. Well, that's basically what most bruisers and fighters get to experience in teamfights currently - unless they are hella fed and none of the other team is strong. Don't believe me? Look at what is played in high elo and the pro scene - tanks and very SAFE damage dealers in vlad or gnar (kinda a tank too) or gp. Jax isn't even played toplane so much - just in jg as a full tank with no damage or maybe triforce for damage. Renekton is unviable. Darius gets kited too hard - if played at all, it's essentially as full tank and he's not dunking anyone after laning phase. Riven can only jump in if her team has 2+ tanky champs who engage and soak all the major hard cc and burst of enemies (like we discussed earlier a good adc SHOULD HAVE TO DO) before she can go in - lest she get cc'd and popped before doing any damage. Think about how much fun it was trying to play vayne or jinx or cait when it was lethality adc meta. Not very fun right? That's exactly what it's like trying to play many FUN toplane champs in a tank or ranged safe damage dealer (like gp, vlad) meta. And that meta is enforced partially because most bruisers and fighters aren't allowed to do proper burst or dps to the enemy backline these days. And to come close to dealing that level of burst, they have to build entirely for 1-shotting adc's or mids rather than build a viable teamfight build - because either they 1-shot or they die instantly for building full damage - a bruiser build with meaningful damage AND durability in teamfights just doesn't really exist anymore past early game.
I can't speak as in depth for midlaners, but let's suffice to say they eventually become irrelevant in terms of damage unless they too can get onto and 1-shot enemy carries. Besides some initial burst from stuff like sion ult plus q combo, tanks should be a non-threat to adc's. Tanks' burst damage should be enough to soften up an adc for their teammates to burst them down with BURST damage, but not nearly enough that adc's have to blow flash or heal due fear of some tank killing them 1v1. But by the same token, tanks and tanky bruisers with proper armor items should not be getting chunked by adc's with no armor pen. If you're hitting a 240 armor 3500hp champ with no armor pen adc, you should be doing maybe 400 dmg per aa at full build when critting. If you're hitting a 300+ armor tank with 4k+ hp, you should be doing 200-250 damage per aa. It's nowhere near that right now. I'm all for rewarding adc's for playing properly, but other roles need to be properly rewarded for playing well too - and currently not all of them are. An assassin needs to snowball early or be irrelevant...moreso perhaps than before and has a smaller window to do so. Most mages not named ryze or cassio lack the kill threat they used to have after a moderate window in the early/mid game. Their window used to be much larger and their mid/late and late game damage still relevant. Bruisers and some fighters are shafted on all fronts - forced into building improperly so they either go for risky 1-shot builds and pray for the best in teamfights or more often build as pseudo tanks - lacking any relevant damage which is a disservice to their name as bruisers, their role, and their purpose. Adc's aren't the only or the sole problem, but they are at the center of a large portion of the major issues with the game right now.