No, this is _not_ a unique situation.
There **_HAVE_** been worse situations with items.
* Black Cleaver of S3
The Black Cleaver you know today was not the original idea. Xyph actually changed it from an old item (BF sword + Dagger) into the tanky DPS item it's "meant" to be today. However, it wasn't unique and FAR more powerful. It was also one of the first items I recall that interacted with AD abilities. Thus, there were games of people stacking black cleaver and nothing but black cleaver.
* Targon Madness of Late S3
Late Season 3 was the advent of the support items you know today...except Targon was insane. Everyone could run targon, the heal was 2% of your maximum health and the execute wasn't melee-only (But that got hotfixed). The sad part is that this actually allowed double melee bot to function for a bit. RIP.
* 4.20 Weedwick
While Warwick was the biggest abuser, the devourer + smite changes in 4.20 caused a surge of people taking this item and becoming unstoppbale gods of the rift. If you had auto-attacks and you could abuse this? Hell yeah you were gonna abuse it. Warwick was jsut the worst offender and boosted his winrate to around 60% win rate. (Yes, even higher than some of the champs you complain about now).
* Sterak's Funhouse
Remember Sterak's? Remember when it was too powerful and EVERYONE remotely AD was building it? Yeah.
* Heart of Gold, Wallet of Platinum
Gold per 5 items used to actually be considered garbage. "Lol u cant last hit so ur getting a gp5 item". Then people realized if you were good at last hitting -and- you got a GP5 item, you were gonna make bank. And there were like four of them. All with non-unique passives. Stacking dank cash money on almost every character.
* The Granddaddy of them All: Zhyona's Ring
Look at this shit.
Look. At. This. Shit.
_And the Zhonya's Statis_
You want to talk about broken? Look at this. An incredible stat efficient item. Offensive and Defensive Boosting. Gold efficient out the ass. To this day, this is the only item so good that Riot had to cut it in half because _deleting it from the game would be too crippling for APs_. If you were AP, you built this. You might even build this because of the statline and defensive capabilities being so good.
Lethality items aren't a new concept. Items run rampant between bad and good all the time. Just please stop saying that "This is OBJECTIVELY the worst time there EVER was when it comes to item!". Because you're wrong. We've gotten through much, much, much worse times in League and there will likely be a time in the future where Riot botches a new item and makes everyone say it made lethality look balanced.