Why is it not true for them? Sales are not magic, it is a profession that can be learned. I have seen a lot of companies stating how important is sales, and how unique they are. It can't be true for all companies. It is like everyone thinking that they are above average, it is just not possible.
If your product is software, literally it is impossible that sales add more value than the engineering organization that builds the product. Without engineering organization, you don't have anything to sell. Without sales and marketing, you will also have a hard time. It is collaboration what brings success.
> There's too much focus by developers on shallow things, like fad-following the latest frameworks, on pseudo-intellectualism or technology-purism
This is usually a problem with recruiting. You get what you pay for. If your interviews are about technical expertise and you ignore basic persona-values evaluation and fit to build valuable features, you get that. And it jeopardizes the viability of a company. You need some really good experts, but you don't need everyone to be one.