I think the original is still the best in terms of open-ended assassination missions and being close to the original vision.
I do not agree that the controls are the best they've ever been. They still lack precision like they have ever since ACIII. The only great addition this time is the free-run descend button, but even that doesn't work well far too often.
The stealth mechanics are garbage. I think they were better in ACIV. Unless you specifically gear for it, crouching does just about jack squat for keeping enemies from seeing you. The cover mechanics are awful and entering/leaving cover is one of the most frustrating things in the game. Enemies are hyper-aware once you enter the first stage of alert. If you get spotted at all during this state the whole area aggros and you start getting sniped from every direction because the enemies, of which there are far too many everywhere, all carry guns that are insanely accurate. Baiting enemies with your "last seen location" barely works at all, and they took out other tools like whistling and moving corpses to make it just an annoying as hell experience. That was how I felt playing the game, at least.
They make stealth a huge pain in the ass, and the controls suck anyway, so what's the best approach to any situation? Barrel in and use a smoke bomb and maybe a medicine or two. Every time.
It's a broken game. You can almost see how they made various parts of it an a vacuum and barely slapped the whole thing together at the end. So many weird features that have no context and no tissue connecting them to anything else. The whole thing is just a mess and the art, visuals, and sound are really the only redeeming features.
Firstly, AC1 was proof of concept. Aside from the assassination missions and pointless country roaming to fight combat-cheesing Templars (for flags, no less), there was barely a game there. No Ubisoft titles in recent memory reach those doldrums. And the assassination missions seemed way more open ended than they actually were, because the designers
didn't program for many ways of approach. I tried them over and over, and the game just smacks you on hand and says, "Nope, wrong way, try again." There were too many which boiled down to: run through a crowd in broad daylight and stab a man to death, then fight off a small army - which you'll be able to do, because you're invincible except for the guard break ability!
That's AC1. Pretty far cry from Unity design-wise, as it should be. It was a mediocre game in 2007 and it's still mediocre now.
If you don't like weight in characters movements that has nothing to with design and everything to do with preference. Ezio was unrealistically nimbler, I'll give you that, but is it really too much to ask of the player to get used to what Unity offers? I played the game. I say no way. It's GTA IV-itis all over again. Rapid descent worked 99% of the time for me. It can look ugly and unpolished with Arno magically snapping to grips 20 feet away, but is it not the developers trying to make things easier for the player? Imagine this game without it and imagine playing past AC games without it. I'd never go back.
I find stealth to be more of a problem if you don't follow the implied paths the developer laid out for you. Unity is still very AAA designed; it's not on the level of something like Deus Ex, and I feel this is ultimately a small knock against it because of the noticeable rigidity. The enemies and level layouts are more of a puzzle than a sandbox. I agree the cover system is too loose and snipers in particular are cheating-ass crackshots.
I just can't behind the extremity of your argument: the game is "broken" and it's "slapped together". Nah. But it is rough around the edges (doubly so for consoles) despite being in the oven so long.