Also, the big elephant in the room here is that the denser housing is, the more quality-of-life for people living there is affected by things outside the bounds

Also, the big elephant in the room here is that the denser housing is, the more quality-of-life for people living there is affected by things outside the bounds of their individual property and the more important it becomes for them to have a say in that. YIMBY campaigners can post all the photos they like of high-rises surrounded by parkland to argue that high-density living doesn't have to be a dystopian hellscape, but when the founding principle of YIMBY-ism is that developers could replace those parks with a blank wall blocking out all sunlight to the residents' windows or an art gallery full of visitors looking directly into their lives all day and the residents should have no way of stopping it that's basically just a bait-and-switch. (The art gallery example and the YIMBY reaction to it is something that actually happened in London!)