I really think people get the wrong idea with NTR. You aren't Robert and you don't have to be, if you wish to insert, insert as one of the other guys. Plus I give major props to the creator and really think the creator said it best, when the game begins he says that the "True End" is the canon ending, everything else is just some what if stuff. Meant for your pleasure. That's probably the most healthy way to think of it. The true end doesn't have any ending scenes in the recollection room which I wouldn't think about too much about.
Also don't pay too much attention to the text, it's mainly there to fulfill a kink. I hold skip through most of it. My only issue with NTR is that it's the "go to" to spice up a story and you can tell when that is the case. That's not bashing anyone, it just seems to be the case that if you don't really know how to give a impetus to your story then NTR is typically the fall back.
A part of me is with you, I don't mind NTR because I know what I'm here for. Though I do prefer games like Makina that just let you corrupt the protagonist no previous relationship needed. I honestly don't know if this game would be better without the NTR. If you were just Ayame who was new to the city. And Robert and all of these other dudes were just paths to the end. And it doesn't matter. The creator wanted it this way and you have a choice. You can rush the "True End" in about an hour or two and that can be the end of it for you. Then you can just unlock everything in the recollection room and continue on about your business. Or you can try and get as much content as possible.