The bigger problem isn't the icon cleaning, bloated feature creep. That's just a symptom of the bigger problem, which is that developers feel the need to make every Assassin's Creed a massive open world game. By creating something that big, you have to keep making up reasons for players to traverse it. The first AC game didn't offer very many reasons, and people complained about it being boring and repetitive. So subsequent games stuff in as much content as possible in the hopes of providing variety. But that too is boring, repetitive variety, with copy-pasted tasks. Every game these days feels like it has to be open world, and yet no game has really satisfactorily explained why.
Remember how Arkham Asylum and Dishonored are semi-open world games in comparatively small maps? And how each section of the map is visually distinct and has its own forms of interactions? That's the kind of game Assassin's Creed needs to try being for once. You get to have all the fun of exploring a city with lots of neat vertical design, but you don't have to wander for miles over the same terrain.
You could set an entire AC game around one major intersection in a city, like around the 5 Points in Manhattan, mid 19th Century. It's an interesting setting because the junction was in the process of transforming from a middle-class hub to a bunch of slums sinking into the ground. Rich looking residential zones transition into collapsing hovels. Pleasure gardens transitioning into quaysides. You have churches and prisons. That's a lot of variety and detail in a tiny location. That physical variety can inspire lots of interesting side missions that are specific to each locale, rather than just a "save the slaves" "collect the transcripts" crap.
