Recently, Bethesda's lead artist Istvan Pely spoke with GamesRadar+. During the interview, he spoke about the approach that was used in the development of Starfield:
We were never going to make Mass Effect and create nine beautiful, fully fledged […] planets, because that’s not the game we were making. We could never have filled the space between them with all that content. It’s impossible.
Instead, the developer explains, Bethesda worked on improving systems "to deliver content right to the player." For fans, "those who really gravitate towards Starfield," it works because "they understand that space is vast — that's part of the appeal and charm."
Bethesda's task is not to slip players a bunch of perfectly crafted planets, but to understand how to help them explore the entire galaxy around which Starfield is built.