>>57526279Exactly, the structure of the game is immaculate. Sure, later games had some decent side areas scattered across the region, but Kanto's basic layout and progression makes it pretty much open world the moment you step out of Rock Tunnel (you also have a tiny open section between Mt. Moon and Route 9 since you can challenge Misty after getting Cut).
In fact what SV tried to do with its open world is copy the three basic principles of Kanto openness - in order to enter the final stretch of the game, you need to a. beat the gyms, b. get progression items (HMs, mostly), c. progress through the Team Rocket storyline. You can do those in any order and they influence each other.
GSC tried and failed miserably and then in the later games you're just walking from attraction to attraction. RGB stands as the perfectly designed Pokemon RPG.