A railroad is not just about what characters can do, it's also about what's going to happen in the world around them, especially when those actions affect the character.
Not by any conventional definition of the word. By definition a railroad constrains players actions. Consequences for non-action are not railroading. A rather silly example for a game about apprentice wizards on middle school might involve preventing the lunch lady from serving brussel sprouts next Monday. A more serious example from the same game might involve breaking out of detention to go watch the big game. A third might involve defeating the playground bully to bring freedom and peace to the ball court. If they don't succeed or ignore the first, they get brussel sprouts on Monday. If they ignore the second they miss the game. In the third, they and their classmates continue too get harrassed and assaulted.
By your reconing, these are all railroads because they have some set of consequences for failure to act. By your definition, life is a railroad.
What about self motivation? That's part of making a character. Characters have goals and objectives even in a world where things don't change very often.
All fine and good. You know who else has self-motivation? Every single NPC, including the villians.
If that happened then you're in the wrong group.
I think it's wrong to say they're not 'engaging in the game' though. It sounds like you're the one who doesn't want to.
I would maintain they're at the wrong table and it's their own fault because I was quite clear on what the game was.
Things change in status quo sandbox games, but it's more often from player action rather than DM fiat.
That's still GM fiat. Changes in 'normal' RPGs only happen because the GM causes them. That may be triggered and determined by player action, but only the GM makes changes. The question you haven't answered is why only the players get to determine this. Why is the GM in your view nothing more then a computer cranking out quests like so much CRPG?
All games are a mix of styles, and some players are more tolerant of differences than others. I think my GM would be equally offended if he created a world, which of course has a story behind it, and I showed up expecting to coast along with his 'plot'.
There's that false dicotomy again. Who said coast? The players have to engage in the plot, follow hooks and leads, address the conflicts, and overcome their challenges. In the context of D&D this typically involves defeating some ultimate personification of evil who may be at any stage of his nefarious scheme to accomplish something. The something here is typically something the players are or will dislike. If the protagonists don't act things get worse for them in some way.
If the players ignore the world, the world does not go into stasis waiting for them to care about it. That's why a status quo world is boring. The players choices don't matter because nothing happens when they aren't around.