Bedrockgames
I post in the voice of Christopher Walken
I'm not saying that there aren't meaningful differences between processes of play. I'm saying that your definitions of "railroad" and "react" are not reified enough to be meaningful. Yes, there are (or can be) real differences of mindset and intentionality on the part of the GMs, but when you start looking at what railroading is as a process or what reacting to the actions of players is as a process, what you find is that there are big overlaps.
I mean if your definition of railroad includes the GM allowing the players to go on unexpected paths, and not trying to keep them on a particular adventure or plot, I don't think it is a particularly practical definition of the term. But even then this is not strictly about railroads but about the posters remark that they let the players make things happen, not the GM. Again if you take that literally, then sure, there is a problem with the statement because the GM is also making things happen and has ultimate say if we are talking about a system or campaign where the GM has traditional GM authority. But it is clearly meant to be about letting the players try to go where they want to go, to set the agenda in the setting by declaring "We go north!" or "Screw this guy, I let's start a bootlegging enterprise in Dee instead of helping this guy obtain the Manual of the Nine Claws". It is about adapting and reacting to the players. If one doesn't find that to be different from a much more story driven "GM as narrator" approach, or even a adventure path built around encounter challenge ratings like you often had in the 2000s, then I don't really know what to say. You can scrutinize it and say 'but the GM is still making things happen'. But the point is the GM is responding to the players agenda and actions rather than just walking in with a game plan he expects them to follow.
I've been playing since 86, so not that far from when you started. I would agree that it isn't simple. Like I was being reductive when I mentioned those two styles of play. However those two styles of play definitely existed and were definitely common in those eras (I know because that is how I played in the 90s and that is how I played in the early 2000s-----and it is how most of the people around me played and it was also reflected in a lot of the GM advice). That said it wasn't unified. You also had people playing much more old school, and even a given GM or campaign could mix things up (I know I changed how I approached adventure crafting in the 90s as the Van Richten books had more and more influence on me for example)I've been playing from the early 1980s to now, and I have to say that the differences in eras aren't as great as some would make of them. It's more about focus or goals or how you maintain the illusion of perfect freedom than it is complete difference in technique. For example, when Gygax writes in something as "primitive" (meaning early and not poor) as G1: Steading of the Hill Giant chief that you can't burn down the steading because it's made of wet green wood, he's applying a railroading technique to achieve some desirable story.