There's like 10 fundamental games such as like Being a DIK / Big Brother / Milfy City and the newbies just copy-pasting and making the story even worse.
Well, this summarize the issue...
The day people will stop to use
Big Brother and
Milfy City as reference will be the day the adult gaming scene will become mature.
Big Brother was kind of innovating at its time, but it's also a "how to not do a game". The game mechanism is confusing, there's near to no hint/clue regarding how to progress and it switched main dogma twice (harem->NTR->hope for harem).
As for
Milfy City, it's ICSTOR (failed) attempt to add a real and consistent story into his usual generic incest games, but he did it by copying the games that were successful when he started it.
They are known because over hyped, but this doesn't mean that they have or had any influence, and even less that they are goods. Therefore, they absolutely don't have their place in that kind of list.
In fact, even
Being a DIK don't really have its place in that list.
Acting Lessons, DrPinkCake first game, is more legit here, but also coming with its well known issue...
If there's fundamental games, it's more games like
Dating My daughter, that introduced heavy narration, or
Dreams of Desire, that introduced strong background story.
Can be added to the list
The DeLuca Family, that is a real turning point in the adult gaming modern era. It represent a pivot point, for the first time an adult game was based over a heavy story including lewd content, and not over lewd content possibly linked together by a story ; and like it succeeded, other creators started to follow. It also was the first one to mix free roaming parts with a scripted background story, offering a double level of progression and giving to the player the possibility to advance at his own pace, prioritizing MC's story or side character's one ; and not it even have a third level with the missions games. All this served by CGs that, at that time, were only equaled by PhillyGames and his
Depraved Awakening, yet another heavy story based game ; one of first ones, if not the first one for the modern era.
Less remembered, because more niche and not really good on their own, are Amaraine's games.
Bondage Island was the first to couple the good old flash "choose your action" with a modern approach for games, without falling into the "trainer" lazy trap.
Damsels and Dungeons, the first to vary the game mechanism, and
Leather and Steel the first real sandbox attempt.
But, all this being said, what is the less accurate in your claim is its last words.
Limiting to Ren'Py WIP games, because let's be honest they are the most played, and without regard for the inherent qualities, how games like :
Ataegina,
Bad Memories,
Desert Stalker,
Empress Games,
Futagenesis Unveiled,
Halfway house,
Heavy Five,
Hot Sand of Antartica,
How to fix the future,
Karlsson's Gambit,
Lust Hunter,
Pact with a Witch,
Space Journey X,
SpaceCorps XXX,
Star Mars,
Star Periphery, or
The Intoxicating Flavor, can be presented as cheap clone of the three you named ?
Those who don't have an effective innovative story have either effective game play, or a way better writing than Big Brother and Milfy City combined ; there's even that have the three. And this is just a really small list that try to cover, more or less, the whole spectrum.
Out of 16000 games, you can't really find 500 projects that you can call "Game".
I'm sure that more than a quarter of the
2,394 Unity and Unreal games, completed or still in development, can be called "games". And this is without counting the Asian RPG Maker games, the, few I agree, Ren'Py games that are effectively games (ever heard about
Sakura Dungeon ? Not like if it's a recent game...), those made with Godot or a purely homemade engine (whatever how bad the realization can be,
Mike Velesk is making games).
It would be really good if people who clearly know absolutely nothing outside of the 5% of over hyped games would just don't try to judge the state of the adult gaming scene.