Meaning(value) is subjective, under capitalism, what's demanded by people is what's produced. Sure speculation can mislead people into valuing the wrong thing but that's hardly a problem inherent with capitalism itself.

Whenever I analyze arguments against the free market, it almost always seems that the person speaking thinks the market should give people what the person speaking thinks they ought to want.

No, what's produced is what the system wants people to think they want. Nobody wants 100 slightly different brands of the same thing. That said, I'll concede that sometimes we don't know what we want (the iPhone for example was a net positive).

You'd be surprised. I live in a country with only a couple brands per product (talking groceries here) and it is abysmal.

Even if they make all the different kinds of, say, cheese (and they don't), the quality is terrible, because they don't have those 99 competitors.

I'm in a similar situation, though to be completely honest I don't mind it much. I lived in a big city with significantly more choices and while it was undeniably better, I don't really miss it.

Meaning is subjective no matter the economic system. Trillions of dollars spent in advertising also misleads people into valuing the wrong things. I see this as a problem of capitalism.

People valuing different things differently is a result of culture. Advertising influences culture, to some extent, but it only wishes it was as powerful as people assume it to be.

Most notably, people are not "misled" into valuing the "wrong" things. You just have a different opinion of what people should value based on your own culture, values, etc. It doesn't mean they're wrong, brainwashed, or anything of the kind.