Jason,
The problem with this and many other articles that discredit MPT is that they offer no alternative, at least in the sense of multi-asset class portfolio construction. If you're speaking purely of equity portfolio construction, then certainly there are many other approaches and I would imagine very few PMs who use MPT in that context. But in the case of multi-asset class portfolio construction, without MPT how do we build portfolios? The vast majority of advisors merely guess, or go with their gut, which leads to emotional decision making. I'm not ignoring the flaws in MPT, just pointing out that there is no better alternative for process driven portfolio construction. Clearly rational decision making is preferable to irrational, and disciplined investing preferable to undisciplined. If we believe that in the long run asset classes fairly price a return for the risk taken, then why wouldn't we use MPT to construct portfolios with long time horizons? Or as I asked previously, if we don't use MPT what should we do?