Idk man you can let both know you’re not interested pretty early and even if you want to do so, there’s still no denying the fact that at this point Geralt has had history with both women. You can role play Geralt to an extent, but you are still role playing a pre-establishes character. So as much as the player has a say in how Geralt acts, telling both of them to just smurf off from the start would be very much completely out of character for him. It’s the same reason why Geralt just wouldn’t work with male romance options. He’s a character that has been established for a long time, throughout a whole series of books and two other games. Not being able to tell Yen and Triss to go screw themselves from the get go is not a flaw of the romance writing - it’s simply taking into account what choice can be given within what we know of Geralt up to that point.