Too me the incest just feels tacked on with title switches, no real reaction from any characters that Max is fucking his entire family
I would say in the first half of the game it had. Alice and Ann are the ones who hesitated the most, also when Ann was teaching Lisa and Max. It is also mentioned later a couple of times, for example when Max and Lisa visit the doc, who talks about them being family and Lisa asks the doc not to tell Ann (ignoring the fact that they screwed in front of her while being filmed by Alice). But you are right, it's not the main focus of the plot. Honestly I find this better than constant "oh no, but you are my xyz." which you find in other stories.
The moment when everyone pretty much accepted what the MC is doing is when games end usually. This one goes on past that point. That's no excuse for the terrible "repeat this event every week 20 times" design, but it's something I can say in favour of the game.