I get what it was added for since AC2. It adds some replay value for missions for those who want an extra challenge. But I'm at the point where I feel like the story is really starting to ramp up and build toward the ending, and want to just let myself figure things out with the systems they have been giving me the whole game at a good pace, and not be having to constantly look around for exactly what the developers want me to do in each particular moment.
I don't wish the system was gone, but I wish it was less intrusive in telling you how you did. That might end up being more frustrating for some people: not knowing the exact moment you failed the 100% requirement, but if I wasn't interested in 100%ing every single little thing all the time and wanted more of a focus on story (at least on main story missions), then I could feel a little better ignoring the fact that I only got 50% and if I wanted to could go back later.
I had the same problem with L.A. Noire and the checks or X's it put on your notepad as you interrogated someone. If they want me to just let things play out and have an option even if I get everything wrong, then why do I have to know what I got wrong right at that exact moment? Of course I get why it's there, so you can actually know what to do differently to get everything right the next time, but it still really broke the immersion for me and tempted me to hit restart.
This could all be me struggling to not be a perfectionist and I know I can just ignore the optional objective, but is anyone else bothered not by the purpose of the sync system, but at how in your face it is at telling you that you failed when you would just like to keep the story going?