Look at Kanto. You can go anywhere after you get Cut, right? Well, not really. You HAVE to go through Route 9 to get to Rock Tunnel so you can reach Lavender, but then you're free, right? Again, no. You have to go get the Silph Scope and do Lavender Tower so you can get the Poke Flute to awaken the Snorlax that block both routes to Fuchsia. You unlock decent chunks at a time, but the way to progess is still fairly restrictive.

Now, let's look at Johto. From New Bark Town until you beat Whitney you can only go in one direction. But once you reach Ecruteak, finally, you're free to go all the way from the Lake of Rage to Olivine! But you can't do anything until you beat Morty, because you need Surf. So you do that, and then an actual choice appears. You can either go to Olivine, surf to Cianwood, beat Chuck, heal the Ampharos, and beat Jasmine, or you can go to the Lake of Rage, catch/kill the Gyarados, do the Rocket hideout, and beat Pryce. Then you do the other, and then the Radio Tower, and now you're back on the one way path to Blackthorn. I'm sure you all know what the issue here is: The level curve. GF had no idea how to balance this, so Chuck and Pryce are of comparable difficulty, meaning you'll find one a hell of a lot easier than they should be, and the rockets even in the Radio Tower are still in the late 20s/early 30s level range. It jumps from there to late 30s/early 40s when you can finally start going to Blackthorn.