Jason,

As a practitioner, the criticism of an investment approach has little value if an alternative is not proposed. I hate the idea of having to eat healthy and exercise to stay in shape, but I don't have a better solution so I am left with the best available advice as my only option. Additionally I congratulate you on your phenomenal track record, but my guess is that your skill cannot be replicated by the broad investment universe, otherwise it would be.

I do believe we are discussing different uses of MPT. You appear to be focused on a pure stock selection / equity portfolio, where I view MPT in the context of a diversified portfolio of asset classes. That may be the key to our disagreement.

I agree with the article's premise that human behavior is a factor that cannot be ignored. But how do we model it? And is it predictable? I would argue that we cannot model it, nor is it predictable. We can only observe it, and manage it with our own clients.

MPT provides the framework for a conversation around goals, objectives, risk tolerance, and managing expectations. Without a framework, discussing the tradeoffs between risk and return would lack substance. Most investors would choose to earn higher returns and lose less money in all cases. Without the ability to quantify a range of outcomes, an adviser is almost certain to disappoint their client at some point. Returns weren't as high as they wanted, or they lost more than they were comfortable with in challenging moments.
Until the holy grail of return without risk is discovered, educating clients about how their portfolios will act in different markets may be our best approach. If there is a better way to describe how portfolio decisions are made or to discuss the range of outcomes in different market environments, I would love to hear it.