What makes you think it isn’t?
But assuming that's what parent was talking about (since that's the only thing they mentioned) - the market is sometimes wrong, for sure, but not as a general rule. If someone is earning a lot of money, they are giving some value that is worth it to the company that is paying them. More money = more value.
This doesn't always track with "contributions to society", because you can do things like e.g. stealing, which "gets you money" but doesn't contribute to society.
But consultancies as a general rule aren't stealing, they aren't as a general rule doing unethical things, etc. They are, for the most part, helping businesses. And that help is worth real money. This isn't theoretical either - if a consultant helps a business be more efficient in some process, that means real money to the company, which means real-world additional wealth is generated, which is a good thing.
The parent just made a quip because (I imagine) they think consultancies are a waste of money. And sometimes they are! But c'mon, I've known plenty of good, smart people working as consultants and I wouldn't want to jokingly quip that their job is meaningless. It's not worthy of a site like HN where we try to actually talk about things thoughtfully and critically.
In a capitalist society, these are basically competing entities seeking to maximise their own profits. This entails minimising expenses. That is, in capitalist society, businesses work to charge as much as possible, give back as little value as possible, and put as much pressure on their suppliers as possible to lower prices.
The argument that this is a net positive for society could use a little substantiation.
I can make the theoretical argument all day, but really, we've lived in a world that has done this experiment for us. I look at capitalist countries, I look at communist countries, and I think it's pretty clear which ones are better to live in.
The majority of societies that have tried anything different were/are significantly worse for the average person. That seems like more than a little substantiation.
Consider the extent of human societies that have existed, what it is that we know of them and through what lens we know of them. What do we mean by the words "significantly worse"? Where does this idea of "worse" stem from? And let's not forget the average person. How do we measure what's good for this average person?
Sorry for the random remarks your comment caught my eye for some reason. The point here isn't for some bogus relativism but merely to state the obvious, that the human condition can be far more complicated than we give it credit.
All the reasons you say businesses suck are also the reasons why they work well. They need to react instantly to market pressures. If someone is making something no one wants they will crumble, if a new demand springs up businesses will instantly be created to meet it. I can't think of another system that is instantly responsive to a changing world and doesn't require much oversight.