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.
Farcry and farcry 2 were my map editors of choice