Why would it be changed if that's the way it really was?
I doubt the placement of sandbags and such is 100% realistic. The basic square can be kept the same while still changing cover of tactical value.
The sewers are also extremely limited. They could easily make the sewer system more expansive and keep it realistic.
Maybe expand the map and include a bit more of the surrounding buildings and make the large square area only one of the capzones and not the "center"?
They can't just throw in some random buildings, it's a historical location and that would be tantamount to blasphemy

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There's plenty of room for placing sandbags and trenches while still having historical accuracy.
There IS plenty of cover though. Just gonna play it slow, check for bad guys, sprint, crawl, repeat.
The problem is, a lot of the cover is only high enough to conceal you if you are prone, since people in 2nd floor windows at the side can look down at you and get headshots. You can't "peak" while prone, so essentially you just have to run to the cap zone and lie down behind a wall or sandbag and hope enough of your teammates do the same thing. This is not good gameplay.
Due to the height of the cover, and the angle of the surrounding buildings, its not possible to look around and actually fight people in the buildings. This is compounded by the fact a lot of the buildings are fogged out which makes them very difficult to see, but people in buildings have a clear view of people in cap zones.
How quickly do you think you can stand up from cover, get a look around at all the riflemen watching you, mark a target, get back down, get up and shoot without getting shot? Given that multiple riflemen probably saw you run for cover and are just waiting for you to stand up.
They either need to increase the height of cover, or add a more expansive sewer system so people can move around more in caps. Also some holes in walls or sewer tops where you can get good shots off at people in buildings would help immensely.