I've played SC since the second installment, and I don't think there is a very big difference in how "easy" it was to ring out someone between then and now, I just think that it has always been really easy to get ringed out if you don't pay attention when you play against someone who is actually good. I think the main thing that changes ringoutfriendliness between installments is how the properties of various characters' attacks are changed, not stage designs.

In SC5 there are also destructable walls on some stages, so which positions are safe from ringouts actually varies over the length of the battle. A wall might stop a ring out once, but then there's a big hole in it where you could suddenly get ringed out now, so you have to pay attention to where the walls are broken.