I’m currently reading the book “Game On!” About video game history, and had to verify.
When initially designing The Sims, Wright spent a great deal of time researching the fan community of the hugely successful Quake and Quake 2. “I was amazed at the time people were pouring into making their own custom levels,” he told Wired. “So with The Sims, we wanted to make it possible to modify everything. Players could use it as a storytelling platform.”
https://www.shortlist.com/news/15-things-you-probably-didnt-know-about-the-sims-4
Building a world was quite novel back then.
Subjectively at least - and this might be rose-tinted glasses influencing my judgment - it feels like it was more common, that certain genres were almost expected to come with an accessible level/map editor. I think I spent more time with the one from Age of Empires than the actual game.
I remember finally getting my hands on the editor for the Build engine after a few years of making maps in Doom and Heretic and had thought 3D level design was only something super geniuses could do… Until Hammer showed it was just the garbage UI/UX of Build lol