Well, I'm currently playing Origins, so here's my thought and a bit of backstory to give some context.
And it goes without saying but let's say it anyway :
All that follows is a bunch of opinions and in no way do I challenge people who do not share them. We can be friendly and disagree about games.
I started playing AC back in the days and was kinda disappointed by the first one but I loved how AC2 took almost everything from the first one and made it better. I liked Brotherhood and Revelation's story but felt their gameplay got bogged down in minigames and side activities that were not needed (tower defense, assassination ledgers)
I stopped playing before AC3 because the setting and marketing didn't interest me.
I've followed the franchise from afar until Origins. Now ancient Egypt, that caught my attention so I decided to play everything AC from 3 to Origins because that's how I roll.
Here's my tale :
I was pleasantly surprised by AC3, so far my favorite story. I loved that neither the templars nor the assassins were in control of history. My only real gripe was the ships and I was glad they were just a side activity that could almost be ignored.
As I said, I like AC's core gameplay and disliked when it brings too much side activities and mini games so it should not be a big surprise that AC4 is my least favorite as it's the most divergent one. To me ship to ship combat, no matter how well done, do not fit playing an assassin (which is what I want to play in an AC game).
It's also the game where they all but ditched the modern story which to me is a real shame.
Rogue was fun. Somehow, playing a templar patrolling the sea made me feel like the ships, as an instrument of templar authority, belonged for the first and last time.
I was very pleasantly surprised by AC Unity and Syndicate. Both probably have the weakest stories but they do have the best gameplay overall to me.
Now to the end of my quest Origins :
I currently do not know what that game is or is trying to be.
Gone are the gameplay progress of the previous games.
Its parkour is inferior, its combat is mindless hack and slash. The mission design is almost exactly the same mission after mission : meet NPC take mission, go to point, scan the planet, defeat a handful of ennemies, find treasure, find target.
Its map is so large that I spend most of my time on my camel rather than actually interacting with the environnement (which was one of the reasons I disliked the ships to begin with).
It has been saddled with one of the poorest RPG implementation I've seen. The skill list is derivative, the gear is just an endless grind. It takes more than 1800 materials to max out compared, for exemple, to about a hundred more diverse materials in Far Cry 4.
And then there's the damage sponge bosses. Adding difficulty by adding hit points is, well, where tabletop RPGs were thirty years ago.
The most egregious stuff to me with that hit point thing is that you can't one shot some "boss" while you can dispose of a handful of crocs or hippos by flailing a sword in their general direction.
It all feels very reminiscent of Deus Ex HR which, as a game offering multiple approaches, had been lambasted for forcing boss fights on the player.
As for the story. Well, it's a guy going the AC way because a family relative has been unfairly killed. I feel like we've already been down that road.
What's left, and the only reason I'm pushing through (outside of my completionist character) is a gorgeous open world.
I wish AC's story and game design guys were as ambitious as AC's environment artists.
(TLDR) Origins to me feels like a beautiful luxurious chair which is oddly unconfortable no matter how I try to sit in it.
I'm currently hunting for the crocodile and hope that something happens to change my mind. But I'm pessimistic.