Maybe we're just not aware of it, but perhaps Soulslikes fall under Metroidvanias... And as we all know, there's an abundance of lewd Japanese games that are basically just re-skinned Metroidvanias (looking at you, Shadow of Yhidra)
There's this really cool open world game that was released around three months ago, you might've heard of it.
The main character gets fucked quite a lot. Plus, there's this one boss that's a triple-amputee (!). She really likes shoving her sword into you.
What's the game ? Don't remember seeing it
Also while I agree that Souls-likes are pretty similar to metroidvanias, I don't like that most metroidvanias take after the "metroid" part (you mostly get different abilities for your character, while your arsenal mostly stays the same), rather than "castlevania" like Symphony of the Night (you find various weapons and tools with different strengths and weaknesses that help you choose how you want to play), which is why I really like this game, because it takes after Souls-like philosophy of your character's restriction being skill-based, rather than equipment-based.
A great example of "metroid-based metroidvania" (ngl that sounds kinda weird) is Alien Quest EVE: there are only 4 weapons, and every one is a direct upgrade from the previous one. Every other item is an upgrade for your character (double jump, speed increase, a literal screw attack from metroid), plus a few magic abilities which still don't count as unique weapons in my opinion.
I should add that I don't hate Alien Quest EVE, it's actually one of my favourite Hgames, I'm just saying that in my eyes there's a bit of distinction between Soul's-like/Castlevania-like metroidvanias (Night of Revenge, Bloodstained:Ritual of the Night) and Metroid-like metroidvanias (Alien Quest EVE, Touhou Luna Nights).
At the end of the day however, both "types" are great and often manage to be either just really good games, or, in Hgames case, both offer great porn content and very enjoyable gameplay.
Sorry for writing a freaking essay on differences between what is essentially slightly different types of the same genre.