Mouseferatu had an interesting piece in one of his blog posts that contained this gem
He's discussing the Temple of Elemental Evil, but I think this is even more relevant for HotDQ. My reading of it makes it seem very sandboxish. There are few things that must happen to progress the story, some episodes more so than others, each problem has so many ways to skin a cat it looks like a hat factory and there are plenty of hooks for trips into the blue yonder. But most of the complaints I've seen about it are that people are feeling conned or railroaded, things I don't see on the page.
Ultimately there is a linear element to it, the pace of the narrative is driven by external events outside the characters control, but to do otherwise would be to provide no challenge. Fall too far behind the Cult and they are lost, that can be hard to recover.
I do not understand how your post relates to mine that you replied to.
I suspect that the Dragon exists in 99% of the games run, good DM or bad DM.
The Dragon, in my mind, is the main problem in Greenest. In fact, the only other issue I have with Greenest is the Half Dragon encounter and that one is merely lame. The rest of the encounters are fine as far as I know.
If we are discussing railroading, I think that the Dragon is a main engine. Players feel railroaded when they do not feel like they have a choice. Good DM or bad DM, I think that some players feel like they do not have a choice and have to go to Greenest.
I don't think that the dragon part of the discussion has much to do with the quality of the DM. It has to do with the quality of the adventure design.
For those people who did not even question their PCs going to a town with a dragon flying overhead, I have to wonder why not? Are you not roleplaying your PC at least to the point that it would be discussed? Or are you metagaming that this as the direction being shown to you by the DM, hence, it's the adventure and it's all good? I do know that in the Mike Mearls video, the fact that a dragon was flying overhead was not even much of a consideration. Course to be fair, it did not look like he had experienced players there.
Mearls also mentions that the town is engulfed in flame. So much for the town "not really burning" posts.

It might not be burning in the module, but I bet it was at some tables.