You have to build and move a miniature Earth ecosystem just to support a person, since the only way to make food to date is with other organisms. Even in a fixed structure right here that's proven hard; Biosphere 2 had to be aborted.

NASA has done all probes in exploration outside of Earth's own system for basically that reason. How does that not come up in an academic meeting?

And vacuum balloons can't be made out of any real materials, and wouldn't solve the gravity too strong to stand in, and carousels exist on Earth, and if it's not cantilevered you should use linear tangential velocity which has to be higher for a bigger ring, and biological systems aren't linear and can't necessarily just be extrapolated out...

Alternate link for that paper, which actually is a good source. I think the last time I heard about (the lack of) progress on the problem was from Zach and Kelly Wienersmith on the Nature Podcast. I don't know who exactly would disagree with the "roughly proportional" take here, but I'd be surprised if that was just a fabrication. Proportionality also brings up questions about if higher-than-Earth gravity would then be better for us.

Anyone reading can find a ton more papers on space stuff through ICES, which looks neat.