This is a tired argument. The amount of land wind and solar needs to power the world is extremely small comparatively speaking [1], and nuclear just can't get built in under a decade. So we use a bunch of land, but at least it gets built (you can build the equivalent power generation of a nuclear plant, even taking into account capacity factor, with solar and batteries in ~2-3 years).

Perhaps density matters if you're attempting to escape a gravity well, but Earth is big and space is not a concern.

Y'all know enough sunlight hits the Earth every 2 minutes to power humanity for a year, right? [2] It's fusion at a distance. Someone else handles the waste, the safety risk, there is no neutron embrittlement issues.

[1] https://landartgenerator.org/blagi/archives/77565

[2] https://gulfnews.com/uae/environment/two-minutes-of-sun-enou...

(i support running existing nuclear generators as long as safely possible, and Germany should start them back up)