He mentions in another article he trained in Karate for over 20 years, and trained with different clubs and within different organisations. He also seems like an intelligent person. He also trained in TKD. I for one can't say whether every single school he went to was a McDojo. He mentions in one school they extensively used a makiwara, which doesn't seem to be something they use in a lot of WKF style classes. For all we know he could well have studied full contact karate and okinawan karate at some point.
Others made the point on his blog that he wasn't training at "the right school", but he maintained that after more than 20 years of karate, karate was simply too time consuming and offered little benefit. I don't think he would've changed his mind even if he went o an okinawan karate school.
And I have to agree with Dysfuctional Parrot's point that karate isn't the best way to keep in shape. Sure, if you aren't active karate is better than nothing, but nowhere nearly the best exercise for stay healthy surely. Even knockdown karate, with severe blows to the head and large potential for joint damage (Mas Oyama had crippling arthritis from a relatively young age) to the possible dubious effects of old school Goju okinawan karate on blood pressure.
One final point: After 20 plus years of karate, and probably having spent a massive amount of his time and money with karate, I certainly don't think he owed karate anything. It took a lot from him and he felt he got little back. Why should he go out of his way to change karate and potentially, from his point of view, waste more time. I know you're passionate about karate Ken, but regardless of style some people who train in karate will have a negative opinion on it. That's life.
"Let your food be your medicine, and your medicine be your food"