Its just a bit of Adult gloss to keep everything a bit juicy. The relationship/sex between my Tav and Shadow I thought was really elegant. It was slow burning and kind of deep which is what I'd hoped for. Would I like to see more and perhaps grittier Adult content? Yes, I would but done with the same thoughtful and not too "game invasive" manner. The world and its magic are the important bit. Sex is there to spice it up a bit. To those that don't care for it, just switch it off and move on.
"Just switch it off" doesn't help when the oversexualization is driving development. No amount of switching it off changes that Larian is spending time and money to add more kissing scenes instead of adding an Omeluum ending. Or that instead of an original character to round out the race and class balance of companions we got "yet another elf" Halsin with several fetishes tacked on as only content.
And it's existence doesn't guarantee that it was done in place of things like an Omeluum ending. Or was the driving force behind "Yet another elf" Halsin instead of a race/class balance.
It's impossible for us to know exactly how much sexualization impacted overall development and even harder for us to know if certain desired additions to the game were scrapped purely because they spent development time on sexualization.
Thus it's not a very strong argument to rely on.
Thats a smokescreen. Resources (time and money) are limited and while we do not know exactly what they would have been used for if BG3 were not oversexualized we do know that with all options open to them Larian decided to pump even more resources they had into romance and sex.