And the producer itself already stated it a long time ago as he described, how they set up and balance the difficulty of the game content. When they balance the difficulty of content, they have a timeline how many players shall be able to finish that content within a specified period of time. He also told, that they modify the content when the numbers don't are like THEY expect.
That alone make it very clear: Not all content is made for everyone, because they design it with the focus on "shall only get beaten by x % of players till day y".
As long they do not change it anymore (BCoB, SCoB), the numbers are like the Devs want it to be.