Hiya!
Er..the story elements woven into the adventure are much more...prominent? Yeah, they are more prominent in'newer' adventure style books (re: 3e+).
Just take one "old school" adventure; L1, The Secret of Bone Hill. Here's the story "There's a ruined castle of a sorcerer just out of town. Around it all the plants are dead or sickly, and skeletal animals run rampant! Lately, people have claimed to have seen and heard strange things...ghostly lights and eerie howls...coming from the ruins". That's pretty much it. There are some 'sub' or 'side' stories that may or may not be taken up by the DM and/or Players that involve other locations, but they don't have much at all to do in the way of being 'integrated' into very many NPC's at all. Easily ignored...either on purpose or by accident.
Compare that to "new school" adventure; Savage Tide. I don't have time to go into the story because it would take too much time. It basically involved certain "absolutes"...like the PC's WILL accept Lavinia as a patron, and the PC's WILL accept her ships, and they WILL accept her as Mayor, etc, etc. And that's just one NPC. At any point int he adventure, if Lavinia is killed or the PC's butt heads with her and rebuke her status...the rest of the adventure falls to pieces. The DM has to do a LOT of work to fix/modify soooo much of what is written that at that point, the DM is probably best in just ripping out the maps and writing his own adventure stuff. Which defeats the purpose of spending money on the adventure books.
I'm not saying this can't happen with the "older" style adventures. What I'm saying is that the tendrils of the "expected story line" for newer adventure design tend to be much harder and annoying to deal with.
All said, however, I'm finding Tomb of Annihilation to be...less "railroady" than I had imagined. I'm glad I was called out about it and forced to spend some time and money to look more into it. My bad!

Even if it does have too much 'story tendrils', the nature of my ToA being in FGII format makes it a LOT easier for me to completely delete, replace, and/or modify sections without having to have an entirely separate book or have hundreds of sticky-notes plastered all over the pages!
^_^
Paul L. Ming