Settlement management is alright. Building is severely limited by the necessity of actually building stuff, and building something custom is often a pain of figuring out how all the pieces work. A building with an indentation needs to use a corner wall, as two walls cannot meet at an indentation, but they can meet at a regular corner.
And don't get me started on having enough generators to actually build proper electrical systems. Custom building is not intuitive, but circuits in this game are borderline impossible to understand past simply connecting things to generators directly. Televisions require power, but they don't need to be hooked up to a power source, or actually require any units of power, they just somehow induct energy from nearby generators. Meanwhile, a spotlight turret requires 2 units of power, but other forms of light require no units of power and just close proximity to a generator, yet they serve the same purpose of making the detection of enemies easier for npcs and turrets, and cost significantly less than a spotlight, which only produces a measly 2 defense. You could build a laser turret with the same energy requirement and get more return on defense.
I've built 3 mega fortress settlements already, and I'm getting ready to setup for a fourth, and I'm tempted to just make it a giant metal tower that looms as high as it can, because it's just not practical to build anything custom that looks good unless you're willing to sit down and get aggravated at discovering new limitations that prevent you from building your super awesome fortress of doom.