Which is the same as saying that fifteen different people might walk down a street at different times and while the experience of doing so might be completely different for each one (who they meet, the weather, the time of day, the smell of someone's rose garden if it's in bloom, etc.) it's all the same in the end because in the end the street itself didn't change and they all got from one end of it to the other.
Everyone seems intent on reframing what I say into something I didn't. It's very weird. If we're talking about the street, then walkers on it are interchangeable -- the street doesn't change depending on who's walking on it. If we're following a specific walker and look at what happened to them as they walked down the street, that's going to be different from a different walker's walk in at least some small detail. Regardless of those details, the walker goes down the street, which is the same for all walkers, and arrives at the end of the street, which is the same for all walkers, and completes their walk down the street. The street, at no point, changes for any of the walkers -- they just make choices to encounter it slightly differently from each other.
I mean, there's a huge amount of similarity to recollections of what happens in CoS for various groups. The story beats are the same. The end goal is the same. Vallaki is the same. Doesn't matter who the character are for this. As far as the adventure goes, who's playing it is interchangeable because the adventure doesn't change based on who's playing it.
This is a desired trait, not a negative one, for the purposes to which APs aim.
You seem to only be looking at the part that says the street is the same and people go from one end to the other. I'm looking at the variable experiences they have en route and saying that's more than enough to consider each person's walk down the street to be a unique event.
No, I get that you're looking at it that way -- I've pointed it out to you and various other posters at least three times already. I'm not confused on this. I acknowledge details change on plays (they change with the same party and players and adventure even, if for nothing else other than the RNG). That was never my point. My point is that characters are interchangeable to the adventure. It's how I can announce to my group "I'm going to run Curse of Strahd," and then ask, "What characters are you making for it?" See the line there -- the adventure is picked and then characters made. Why? Because you can make and bring whatever you want, the adventure will still have the same challenges lined up. The difference will only be in the particulars of how a given group overcomes them. This is good fun, btw, and I'm not knocking it. I'm pointing out how APs, and much of 5e play, literally doesn't care what characters are present to try the challenges put out by the GM. It's not a game that does this. There are pros and cons and you absolutely can have loads of fun doing it -- I mean I still play and run 5e so I'm not against this idea at all (obligatory reminder I'm not a "you hate 5e" person). It's how the game is built and how it works. There are other games that don't do this, though, where the idea of an AP, or a main quest, or a side quest are just not.