Assassin’s Creed and the Open World Gameplay design. It definitely existed before then, but after AC came out, it felt like every RPG switched to the open world map.
There have been "open world" games since the 1980s. Just of course, memory limited how big that world could be, and how much you could do in it. The genre as a whole is ancient.
The first ones I can think of is legend of Zelda and final fantasy, but I think there was also Adventure for the Atari before those even. The first Assassin's Creed was 2007, Adventure was 1980
It hasn't aged too badly, but it's from an era where you were not necessarily expected to figure everything out on your own -- talking about it with IRL friends or reading tips and tricks in a magazine (or on the early Internet/Usenet) were pretty normal. I would say give it a try but don't be hesitant to look for a guide if you get stuck or lost.