Realism is a set of immersion. When people argue that something isnt realistic they are meaning that the way something is placed ingame its breaking the immersion of realism.People pull up realism whenever they have no argument to make. It is not brought up with any mechanics they enjoy. I mean, who's complaining about having a horse leashed by the town indefinitely at no upkeep? If a good mechanic is added, being realistic is just a nice topping, not the reason why it's good. Realism is also mentioned a lot when what is really meant is authenticity and/or immersion. And an entitled mindset is another thing. "Huh, I would've thought there'd be onions in a market" and "It's so stupid there's no onions in the market" express the same issue, yet with different openness to an explanation. One would think the concept of game design would be a sufficient explanation for decisions made for gameplay but I guess some people prefer to be angry than to think.
Theres immersion of magic, immersion of horror, immersion of simulation and soo on. All of them are just aspects of immersion based on a set discipline in our case realism.
If your game is a gritty horror survival and your way to obtain a resource is to get a phone and simply order it in the middle of a zombie swarm then that is breaking the immersion of horror.
The game doesnt offer much that would place it outside of immersion of realism as explained. Its a typical small town, set in somewhere around 1990 to 2010. People are horny, there are hallucinations of beast people but nothing much that would make me say that there are fantasy elements that would mark the onion issue fitting into the world.
Having gameplay reasoning doesnt make issues go away but it seems like some people are more entitled to belittle the complaints of others than to think reasonably about what exact is the problem here.
All they need to do for this little issue is to change the onions into something thats actually rare and the problem solves itself, instead you are trying to argue that instead of doing something that simple people should accept flawed gameplay reasonings.
On a note:
"If a good mechanic is added, being realistic is just a nice topping, not the reason why it's good." Meanwhile theres an entire genre of games aiming at realistic simulations where the reason why something is good is because its realistic not because its a good mechanic.
I bet you will try to come at this with some witty remark "play those then". Ignoring the principles of proper immersion building in favor of your own opinions.