IMO that's what people need to focus on. Is the relationship between the player and PC a friendly one, where they're allies, or is it more adversarial? Are both ways of playing satisfying? <- That's huge, because in many games there's technically more than one way to play, but one style has next to no lewds. The best lewd games give you appropriate h-scenes based on your playstyle rather than forcing you to win, lose, or do either of those in one particular way.
Yeah, it's the kind of thing that people that say "it's just a game" can't quite get. It's a little more complicated. Though I've never been super mad about the MC doing something I don't like, I usually chuckle and say "Oh you fucked up there, you should have done what I was thinking, stupid", which, unless it's absolutely jarring, does help make the character feel more like a person.
I was playing Sunset Overdrive a few weeks ago and the MC is quite relaxed and has a great attitude about the mess in the game. They are friendly, sarcastic, break the fourth wall and don't really take the threat seriously, even when they are getting shot they are making jokes about it if you (the player) keep fucking up.
It was a great experience, I played as a female, and I could really see her being a cool-ass friend, especially since she would directly complain to me or make random comments, even telling an NPC to thank "them" for the good work while pointing at the camera, with the NPC not knowing what the hell they are talking about. I kept thinking "girl you're so cool". Amazing game by the way, recommend it for sure. And that was a character that already had a personality.
Now, I also played Fashion Business. The main character is such a bitch all the time and I hated that attitude, but I also kind of wanted to see how she would react to both lewd and non-lewd situations. There are many ways to do things in that game and I did enjoy that even though I didn't like her attitude. Kept saying "See that's what happens when you are a bitch all the time, Monica."
Another good example is Claire's Quest. Game is great (though I hope it gets proper finished one day) and you are allowed to choose what to do. Now, I like Claire, she's cute, so I actually tried to make her go from little innocent girl to badass, experienced lady that would definitely not use her body to get anything, and it went well. Scenes often show that. Same thing if you go full lewd. You can even mix it up. And in all those styles, she has a different attitude. I appreciate that.
In porn games you would think putting some random hottie and making her slutty would work, but it doesn't, I need more than that, which is why I do like being given choices, corruption mechanics and actual scenes that change depending on your approach. So yeah, it's definitely more complicated than just self inserting or not.