It makes a radically beneficial structural change, while still being easily understood by anyone that’s used to capitalism.

Yeah, that's important. It also doesn't require a revolution to attain, just reforms of the current system. Admittedly, reforming the current system would be hard, but theoretically it wouldn't have to be bloody. I think some people who have never questioned the economic and political system in which they grew up can't even conceive of anything other than capitalism. Other people who have thought about it would worry that any attempted revolution might fail and we'd fall backwards into something much more like feudalism if not outright tyranny.

it’s important for everyone to have somewhere they can exist without having to get permission

Yeah, as bad as Feudalism was, at least serfs couldn't be kicked off "their" land. They were tied to the land, so they weren't allowed to leave, but the manor lord also couldn't kick them out.

As for all land being owned, it is, and it isn't. In commonwealth countries there's a lot of crown land. In the US there's a lot of government owned land. In cities there are a lot of city parks. In a sense all that land is owned. But, in another sense, it isn't. It's land that nobody's allowed to build anything on, unless we collectively (via our reps) decide they are. In practice it's not that simple, but in theory it's effectively land that isn't owned, at least by individuals. I've often wondered what effect it would have on homelessness if there were land in cities where everybody was allowed to live if they wanted. I imagine it would basically end up as a favela. Not great, but probably better than homelessness.