I see it differently, IMO most of the time that logic of "if I had just done that" or "if I has just said that" comes after the facts and usually when you are thinking why it went wrong. To me that's an oversimplification of people's behaviour and motivations, but it's a very common and present narrative that you can clearly see when people talk about "what ifs" for single historical events or overestimate the importance of the actions of one important historical guy over all the stuff going on in the background and the myriad of things building up leading to the final result. I am quite skeptical of the "one chance" or "destiny" narratives.
But, leaving that aside. My main problem with the writing is not the final result (Ian and Cindy not happening), it's the inconsistency on Cindy's reaction to the same thing depending if you go to the book fair or not and the writing, or rather lack of writing, leading to that final result. If you choose to go with Holly, everything related to your previous interactions with Cindy suddenly dissapears and that's specially jarring on Ian's side of things. There's not even a follow up with Ian asking about how the birthday went and there's no more Ian showing attraction for Cindy when he had just been wanking to her photos literally a few days before. The game uses an "if-else" programming logic, not real person logic.
Also again, the split between Cindy's path and other LI's path could have been done so much better (in writing terms and limiting branching terms) if Ian doesn't go to the party because he goes on a sex weekend with Alison. Maybe even better, if he doesn't go because he is invited by Emma to go to the political march and he accepts, potentially opening up a "dating" path with Emma and even a possible future conflict with Seymour. It would have fleshed out more Ian and Emma relationship and deepen Ian's political position making it easier in future chapters to link Ian's story with the upcoming mayor election.
