But this isn't about societal norms, it's about what the girls would want. Sure they might not mind the MC fucking around, but at this point pretty much every developed romance option has expressed a desire for something meaningful with the MC and it doesn't feel like they'd be okay with sharing THAT.
The superhuman argument also doesn't make much sense, especially for characters like Alice and Ella, who are also corrupt and powerful. I really doubt that 'MC is so cool and strong one girl is just not enough' would work for them.
Though to be fair, I do agree with the harem route being endgame here but kind of due to the opposite reason. As in I don't know about us getting any sort of epilogue, and with the way things are right now it's likely that no one will really want to engage in relationship drama and just take what they can get with the ending leaving us to speculate how that might or might not have to be resolved in the future.