No. "Consumers" protest high prices, bad service, or whatever it is they are dissatisfied with, by voicing their dislike to the provider and other people alike, then not buying the product. Otherwise there is no feedback to the provider, they have no idea why the consumer choose to refuse the product, or even if the consumer ever even noticed there was a product to begin with.
I'll give you that consumers should voice their dislike, but it makes no sense when the consumers are the very same people who asked for the goods they are producing. All the people who are complaining that this DLC is 'content-lite' (That is disputable, but not part of this argument. We can assume that the DLC will have an impact on any solitary game of CK2, and thus will last as long as that game would).
Here's a comparison: I paid roughly €40 for the content in the original game. They demand €5 for what is a pittance of that content. It isn't a reasonable prize.
What's more, your "go buy that other thing that costs you less" logic doesn't apply either. Games aren't milk, I can't just go to another store or brand and get a cheaper bottle of the same stuff - not only are the games unique products in general, I certainly can't buy DLCs from any other producer than Paradox. Especially true since there aren't even any other developer making the kind of Grand Strategy games Paradox does, they have a monopoly on their niche.
So, from what you are saying here, the players who are entertained by grand strategy games can
only be entertained by grand strategy games, and thus it is impossible to compare the entertainment you can get from CK2 to any other title out there that is not also grand strategy?
That is just a silly statement to make. Of course you can compare how much entertainment you get from one game to another. You can compare how much entertainment you get from a book or a movie or anything else the same way. At the end of the day you are buying games because you have time you want to waste and want to get the best valued entertainment. After all, if you didn't have time to waste how do you have the time to play games in the first place?
Since you can measure the quantity of time any piece of entertainment can take up (i.e. the time you spend interacting with it) and you can measure the price, finding a number that takes both into account is entirely valid (The number could measure fun too, if fun was something that could ever be measured ever)
Once we establish how much you(general you, not specific you) are willing to pay for an hour of entertainment, then it is easy to tell what is a good value as far as a game goes, or even a movie or a book. It has nothing to do with you being able to purchase the same product at the same place (we are not talking about brands of milk here) it has to do with having alternatives. So what if the DLC isn't something you are interested in, do not buy it! So what if the milk you want to get is bad today, do not buy it! Unless you have a specific need for it (i.e. need the milk to bake a cake, which kind of makes milk a bit of a weighted example because it has uses beyond simple consumption, which is all a game is good for) you don't have to buy it if it's not worth it to buy it.
A much better example for games-as-food would be going to the store, seeing they are selling pizza for more than you want to buy pizza for. Well you really want
something to eat, so you decide to buy a steak instead. Sure they might not taste the same, but they both fulfill the same 'need' (hunger, versus the need to waste time).
It's not about games being simple substitutes for each other but about games being alternatives to other games. Don't like the $5 DLC they are making? Don't buy it, instead go buy a humble bundle and get a lot more entertainment out of your $5.