I disagree with almost every one those points.
1) It does start slow, but that is more or less a tutorial. As far as the "ending slow", I've already explained why they do that and why it's a good thing.
2) It's a good long game of at least 30 hours and if you go into the free roam with some friends it's a really good time. I must have spent a good 20 hours doing that. And, the multiplayer was even okay. I'd say I got at least 50 or 60 hours of play out of the game which is good for a game that is not focused on multiplayer. Beyond that, it's one of the few games that I've ever even considered playing again.
3) I have no issues with those animation. They are necessary to lend some realism to the game. And, as far as skinning, you can almost auto skin if you position your horse over the kill and press the button to skin while on the horse.
4) I had no issue with when and where the game saved so I didn't care that I could save exactly where I wanted. In fact, I though it added to the seamless nature of the game and kept you in the game world better. But, now that I think about it, I think you could save it when you wanted, but the auto save worked so well I didn't see a need to use it.
5) I though the side missions were fine and they are optional so you don't have to do them. Even with out them, and I did not do all of them, it's a good long single player experience.
6) You could go back and loot the bodies. Beyond that I don't see why you complain about having to do that and then complain because you think they won't let you do that in some situations.
7) I'm not sure what challenges you are talking about.
8) The outfits are optional and they do actually add some abilities depending on the outfit. Plus, some of the look cool. I don't know that I need more than that they make it look cool. I guess they could have left the option of changing outfits out, but I don't see how you can peanalize them for adding a little something extra to the asthetics.
9) I tend to agree the mini-games are boring, but they are mostly optional and you don't have to do them unless you want to. I think there is only three missions that require you to play a mini-game and they were short and not an issue. It's just extra content that you can do if you enjoyed it and some people did enjoy it.
10) I didn't have any issues with Deadeye.
Bonus 1: The different weapons did do different things. I noticed a major difference between the pistols, various rifles and shotguns.
Bonus 2: You are seldom forced to ride a long distance and when you were, it was actually fun. Besides, I enjoyed riding around hunting for game and collecting skins. I didn't start using fast travel until late in the game.