I’ll preface this by saying that this is my personal opinion and it’s in no way representative of how Ace gamers (or even gamers in general) should evaluate their games.

TL;DR: the game actually develops the characters and their relationship, which in turn makes me care about them, which in turn makes me tolerate their sex scenes. Meanwhile, many other games that treat sex as a prize take the easy route: they give you a checklist, and if you complete it, you are “allowed” to see a poorly animated sex scene with a character who doesn’t care about you in the slightest and is only there to arouse the player.

LONG COMMENT: For me specifically, it’s a matter of context, mood and consent. While I’m still not exactly comfortable with sex scenes, even in a game like Haven, I didn’t hate them because they felt natural and coherent. They were not a “reward” for me, but a choice made by the characters.

I’ll use Mass Effect 2 as an example of a game whose romance options I didn’t like. I never felt like the crewmembers were actual people, because they never did anything on their own. They stayed in their room doing… nothing, like they were part of the ship’s furniture. There was a stoic soldier, and an assassin with a conscience, and a hardcore vigilante, and even a badass warrior-nun! It didn’t ultimately matter, they never did anything. But as soon as I stepped into their room, they’d start unloading their sad backstory on me, like I was their therapist or something. They never showed any interest in me whatsoever; they barely knew anything about my character beyond my name, but I was expected to care about them, for some reason?

After a few such interactions, they’d ask me to do a job for them (tied to their sad backstory), and after that, they’d suddenly go “hey, we got a lot of chemistry, want to bang?” like it was some kind of reward. Congratulations, Player! You visited this character enough times, picked the correct dialogue options to keep them talking about themselves, and even completed a risky mission on their behalf: you totally deserve the steamy hot sex scene!
And if you do, they do… nothing, ever again. They become part of the furniture of the ship - but this time it’s permanent, because there are no more interactions with them.

The game doesn’t care to take your relationship in any meaningful direction, or better yet, it isn’t building any kind of relationship between them and your character in the first place. It was all in service of the hot steamy sex scene.
Sex is the prize, and it painfully shows in the way the dialogue is written. It feels… icky. Dishonest. I was turning everyone down at every opportunity, as if I was Matrix-dodging their heart-shaped bullets, because the game made it very clear that everyone was down bad for my character. But it also felt like the game was constantly second-guessing me, asking me if I truthfully cared about those characters, or if I was doing what I was doing because I wanted to reach the “prize”.
It reached a point where I stopped interacting with a character altogether because she made me deeply uncomfortable (it was the second-in-command/crew therapist: in our very first interaction, she told me she wanted to bang me; in our second interaction, she informed me that she thought the insectoid guy I had just recruited was hot stuff and needed to get laid).
The game also has a Codex, and the very first entry is “This is an all-female alien race. [Infodump on their sexual life]” which would almost be hilarious if it wasn’t for the sexist connotation. Like, I could go on for days about the many ways ME2 made me feel uncomfortable during my playthrough, but I’ll stop here.

In Haven, sex is never treated as a prize: the player is not tasked with doing stuff to unlock the sex scenes, and the sex scenes are not used to titillate the player. There are dozens of unique interactions between Yu and Kai - some of them playing games or being goofy, some of them doing mundane stuff like cooking or taking a shower, and some of them having sex - because sex can be a (meaningful) part of a romance, but it’s not the only component of a relationship.
The way they talk and interact shows that they like and care about each other. I was willing to “accept” the sex scenes because it was what they wanted, not what I wanted; It was a natural development of their relationship and not a “prize” that I achieved by pressing buttons on a dialogue wheel. Whereas many other games lack substance and depth, and have shallow relationships built on a fake score system which tasks the player with increasing the meter by doing arbitrary stuff, which then culminate in a sex scene that only exists to arouse horny teenagers and leads to no meaningful development in the relationship, Haven builds the relationship first and foremost, and keeps developing it for the entirety of the game: sex is one of many possible interactions between the characters, and it’s never something that you need to achieve, but something that happens naturally and organically because the two characters really love each other.