I wanted to talk about this too but wasn't sure how to do it. Think about some of the older ADC.

Not the strongest in any aspect, but has her own strengths. Vision and map play, her ult transformed any team composition she played in. Until characters like tahm kench came around, and spellbook cleanse, now she's literally worthless. But the way her IDENTITY existed and shifted the game.

A relatively strong early-mid game, but he transformed as a hero once he hit 6. This is the Corki kit that everybody liked, the constant zip zap shoot 'em up always be poking. But then stuff like constant overhealing and shielding kinda made his low poke numbers meaningless. But the way his IDENTITY existed and changed over the course of the game. From strong, to really strong, to weaker than an average ADC.

True damage on multiple auto attacks, but only ever on one target at a time, it lacks fluidity but has purpose. The closest to an assassin the ADC role has, I would say, more so than twitch. And she has a very obvious point of power as well, when she uses her ultimate, her real slipperiness is unlocked. And it lasts a very short time, and she goes back to being relatively less executable in most situations than other ADC's, who can simply "hit whatever's closest" without actually worrying about how that ruins their dps if they change targets. Hurricane almost completely bullied her out of the meta because it's optimized against her.
Obviously, his identity has remained well in tact over the years. The "no crit" adc who excels by just being annoying. Useless from behind, oppressive from ahead.
Yet I came to the same realization when I got to

His identity exists from lvl 1. Just get stronger when you press this button. What? Why is that fun or exciting for anybody? His R has gone from "Trinity force kog likes to weave spells and attacks" to "never cast this really" it doesn't influence his playstyle whatsoever. And that's because he has no playstyle. There is nothing you can do as a kog'maw to distinguish yourself, because all immobile ADC's have to worry about positioning. Every Kog'maw simply presses W. there's nothing.... else. He just always gets better, so why take a character who has spikes, or peaks, when you just _scale with the enemy? _