It is constructive criticism to point out that the premise is flawed and could use a bit of in-text work to fix. There's a ton of good suggestions in this thread for many different takes, even. However, you're setting up an argument here that it doesn't matter what the story premise is, it only matters what the characters do after that. There's a lot of truth that the adventure is really going to be what the players make of it, but absolving the adventure text of any requirements by placing the onus on the players isn't how it actually works. The adventure sets up situations and the players react, true, but it's not in a vacuum -- the setup directly influences the player action. You can point to suspension of disbelief, but this isn't something to expect, it's something to facilitate. You have to do the work so that the suspension is easier, not just expect suspension to anything you put out and then blame the players for failing to suspend.
And here that's the crux of the issue -- the premise setup is such that it doesn't facilitate suspension of disbelief. What I mean by that is that the premise situation lacks explanation that allows it to fit with the experience or knowledge of some people. It actively fights against that experience and knowledge. Fantasy is allow about doing this, though, but that's where facilitation comes in -- you have to provide a reason for this violation of expectation and understanding. It's not hard, fantasy does it all the time, but it's also not done here. The depth of winter has lasted 2 years, with no direct sun, but life isn't apocalyptic -- it's surprisingly normal. Not completely normal, but surprisingly so -- taverns are full, populations aren't crashing, there's still living flora and fauna that isn't water based, and so on. This needs some kind of explanation, or a change to the premise, to assist those that have experience or knowledge that this is a profoundly odd occurrence. And, this lack of facilitation to suspend disbelief can be a problem for some to get into the adventure and have the fun of finding out what the PCs do.
Now, people can do their own work to fix this, absolutely, but that's not a defense of the text. It's an expectation of our hobby that we are expected to fix problems like this on our own rather than expect the writer of the adventure to do it. And, in some cases, this is absolutely true -- if my table has certain uncommon or special considerations I need to do the work myself to adapt. Also, if I have a non-standard table in some ways (larger or smaller than the average party, different class compositions, etc.) then that's also special to my table and I should expect to do that work. Essentially, if it's something at my table in how I play the game, then I should expect to have to do the work. This is absolutely true. However, I shouldn't also be expected to fix issues with the core premise of a module when that issue is apparent to anyone recalling high school geography or happens to live north (or south) of about 50 degrees latitude.
I'd also like to take this opportunity to address that argument that this problem only really applies to modern sensibilities about just in time food. That's not at all true. If anything, just in time food would make this problem easier to deal with, as the logistical network that allows that would also immediately notice the disruption and react due to the interconnectedness that such a logistical network requires, making sure food arrived despite the costs. No, the argument against the adventure's premise, as far as I've seen, has never once been based on a modern food distribution assumption in any post except those knocking down this strawman. Instead, historically, food stores for the winter where limited, both in kind and quality, such that even a late spring or a poor harvest could cause malnutrition. People didn't stockpile against a year long famine anywhere, ever. They didn't stockpile against even a bad year. If you can afford to store a year's worth of food, and do so continuously (replacing the rot and loss to vermin), then you can easily afford twice your population. Now, if a situation is expected occasionally, that changes things, but a two year long winter with no direct sunlight is NOT that condition (and the adventure says this), so the expectation that people have stored that much food against an such an unforeseeable outcome isn't relying on modern food distribution sensibilities, it's looking directly at how food storage up until that has worked for the entirety of human existence. It stops at modern food distribution, it's not based on it.