I am not inventing railroading. It's been a "bugbear" for as long as there have been RPG adventures. And, yes, WotC has done really well with "illusion of choice" style adventures since 5e came out.
If you dig through old threads on this very site, about 10 years ago illusion of choice was all the rage and we were all debating its merits and discussing how to do it well.
The reason: it's less work. It makes the game flow more smoothly along narrative beats, which people like. But it isn't the only way to run a game and it doesn't mean actual choice is inferior.
On the subject of notes: there's a lot happening in a complex open world and players who take notes are rewarded for it when they discover connections. If there is an insidious cult slowly indoctrinating all the noble families, for example, the players suddenly realizing it the third time they have to engage with courtly politics is far more satisfying a reveal than the GM saying, "It's time for the evil cult adventure!" True player agency isn't just deciding whether and how to deal with the cult, it is being engaged to the point of seeing it is happening prior to The Night of Black Blades or whatever.