First, blood and murder - this is already adult content. For images of blood, organs (the brain from the first scene), the game already increases rating. Secondly, if you are talking about sex, then Lae and Astarion scene still being worked on, I assume that they will have cutscenes similar to Minthara scene. Does that seem to be enough? This is not a porn game, you don't have to wait for a porn scene every few minutes or rude expressions like in Cyberpunk.
To be honest this is why I don't really like CD Projekt works. It is not necessary to make everything vulgar.
You are talking about gore mainly, not sex. Sex isn't vulgar, it's part of everyone's life and quite beautiful (or not if you belong to the approximately 2 % of asexuals). I don't want a sex scene on every corner, Witcher wasn't like that at all and I'm clearly not talking about silly porn games. Let's be reasonable here. CD Projekt did an excellent job on Witcher 3, they messed up with Cyberpunk. Check the sales of Witcher 3. You simply can't debate the overwhelming success. I very much enjoyed Witcher 3 and so did Millions! Nudity and adult content made up a significant part of this success story. There isn't a single scene in Witcher, which I consider to be vulgar except for the whore scenes. That's just low, but it's ok that these are in the game for those, who want it.
About The Witcher 3 ... Every NPC girl treats the main character as if he is the center of the planet, everyone wanted him and made it clear. I'm not talking about 18+ scenes right now, I'm just talking about what it looks like. It's bad. It was unpleasant for me to see that even a random merchant for some reason want this man-mutant who is described as something.. bad. In the book ofc...
To me the game is not dark or adult. Their are some society themes, but I don't by default consider them mature. The quality in writing has more to do with maturity than anything.
A kid can bleed and fight in school from bullies and will always find porn around puberty whether you like it or not. Not to mention, at least when I was in school, biology classes start early and are mandatory. Its how things are handled that marks maturity. I think the same concept can be applied to stories. It's not the theme, but how an individual handles the theme.
As for sex, lets not pretend Laezel and especially Minthara are options for normal straight dudes. They are both specific niche fetish's. So let's not go there. Only Shadowheart so far is an option and she is not a swiss army knive of romance. Lol. Not that I'd want her to be.
In highschool I use to tutor at a couple of schools. The elementary schools kids were nastier and more knowledge-able than most adults, but lacked understanding in how to handle most things. Oftentimes I find older people the same way. Only difference is school is now Company or Firm and people are a lot less brave.
I understand what you say about Lae, but I don't understand what's specific in Minthara. Apparently, she already has a fanclub. If she doesn't suit you as a person, it doesn't mean that there is something repulsive about her appearance.
It is not necessary to add sex to every romance. I think a romantic moment like Shadow's kiss really for her personality, and there's nothing wrong with that. Game still has enough sex, violence, and blood.