As a marketer, do you think the so called "content strategy" is any different than the traditional promotional marketing mix? or is it?

I believe that content strategy is more focused and product oriented than the marketing mix. The marketing mix could be more generic and also more systematic in terms of application.

Of course, because a successful content marketing focuses on the human stories, which clients are able to feel identified with, not on how our product/service/brand can be better than others from the competitors. It's and indirect way of making marketing through social relations, so it must be made of feelings, chatting, perseverance, entertainment, report,... when our potential clients need every of each... just like a friendship works.

No dought Contenet Strategy is valuable and must necessary for good markeeting.

Whereas the marketing mix is geared toward selling the product, I believe the content strategy is geared toward selling the product's story and experience. 

In the marketing mix, the price, place, product, and promotion try to make the product more appealing and reachable to the consumer. 

The content strategy, in my opinion, is telling the story and purpose behind the product in a way that the consumer can relate to.