Similar techniques apply today. Pregen like 100,000 stars. Give them names and locations in the galaxy, treat them as your "locations of interest" with a seed. The rest can just be another cloud of particles with no interest and if the player visits, you can RNG whatever based on the seed. No two systems can share a seed. They can, however, share a branch.
What I was never clear on was the degree of cherry picking they did. There were 800 worlds on something like nine disks, each unique and peppered with minerals and artifacts.