If you have to explain things by comparing our formation to something dissimilar to our own to explain how they work together, chances are they don't actually work together. I won't get into whether or not I think they did, as that's not what I'm arguing, but that is such a structurally weak argument that I had to point it out.
I didn't
compare formations, just stated for the sake of argument that he plays in line with Matic and that they wouldn't even collide in 4231 with Fabregas as #10. They don't collide. They didn't at Barca, they wouldn't at any given formation and system (assuming coach of any competence).
Fabregas did fail utterly in big games. Slow as hell, lethargic in his passing and in front of goal, inability to beat his man, and a large tendency to vanish for large portions of the match, regardless of where he was played.
You literally described Iniesta in almost every big game Barca/Spain lost. Every single instance you wrote here I'd attribute to recent Iniesta: slow, lethargic in his passing (ball hogging), tendency to vanish for large portions of the match, I'd add very weak shot and accuracy.
Come to think of it, you really have to dig deep to find a game he played worthy of his reputation (one of the best midfielders ever).
Also, I don't know why you bring up inability to beat his man in context of Fabregas. That was never his playing characteristic and general strenght, it's like saying Iniesta doesn't win headers or something like that.
Iniesta, on the other hand, consistently beats his man, consistently sends balls to our forwards, and almost all of our play on his side goes through him, at all times.
Whoa, high level delusion right here. He didn't do either of that consistently good, especially in big games. Yeah, we saw his brilliance occasionally, but you really have to be delusional to say he was consistently good (especially in big games).
If you think Cesc played on the same level as Iniesta in his time here, you're the one who has a problem, not us.
Yes, I do believe he played at least at the same level as Iniesta when he was at Barca. He did produce honey in last 3 seasons, while Iniesta really showed signs of decline (BOTH at club and international level) in last few seasons (not that he was bad generally, just not his level).
I'll say it again, my general point is that the reason Barca failed in big games is because the whole tactical approach was exposed, not because of Iniesta or Fabregas specifically.