I agree that building a custom CMS is not the right answer in most circumstances. I'm not advocating building custom CMS. My position is that what has "always been a good candidate for an off-the-shelf CMS" is evolving. The traditional CMS will be losing ground at the high and low ends. On the high-end, long-form content organizations striving to differentiate are building their own systems focused on collaboration and content lifecycle features and, on the low-end, static site generators for custom websites. There is a middle, but the middle, over time, appears to be shrinking.