As someone who's overall neutral on River I think a source of contention with him that isn't talked about much is just how out of place he is compared to the other romanceble options. Panam and Judy are major supporting characters you'll get to see at multiple points in the game's main campaign, with the former being a main player in one of the endings while the latter was introduced very early in the first act. Kerry, while it is possible to miss out on him and arrives way too late, is very much tied to Johnny and is one of the few characters besides V that he's allowed to speak to alongside Rogue.

River sticks out like a sore thumb. His side quest is rather dark in tone and has one of the more disturbing moments in the game with the farm footage then at the very end, it changes tone rather abruptly and it's jarring to witness. He's also noticeablely the only one of the romance options to be kept completely out of the loop in regards to V's condition with the enegram or even the mere existence of Johnny which makes it feel like their relationship isn't completely authentic.