It’s all about kids.
Without kids in the picture sure, go ahead, make cities look like Coruscant from Star Wars.
The instant you have kids you see how important open spaces safe enough for unstructured minimally supervised play are. Without spaces like this all you have are kids drooling on Roblox and YouTube all day. There’s nothing for kids in an urban core.
Those spaces don’t have to be undeveloped or even outdoor but I have yet to see a city successfully create an environment safe enough that I’d let my small daughters run around.
So while I agree that zoning is dumb and complicated, I also think it’s important to understand where people are coming from.