Forces ought to be designed explicitly to fight under conditions of uncertainty and to achieve effectiveness rather than efficiency. This will entail tolerating a higher degree of redundancy.
I suspect that the above provides the meat of McMaster's article.
I see his "conditions of uncertainty" as another way of describing risk. The level of risk is a factor of the degree of damage caused times the probability of occurence. Risk can be mitigated but it cannot be eliminated. Force design is (or ought to be) a function of trying to mitigate risk in the attainment of assigned missions. One way to mitigate risk is to overdesign for contingencies. This is what McMaster seems to espouse with his desire "to achieve effectiveness rather than efficiency." However, force developers must also recognize that not every mission has an equal probability of being assigned. So, the force structure must be such as to be able to handle the missions whose risk (consequences of failure times probability of occurence) is highest, within availalble resource constraints.

The real issue is whether those who drive the budget process are willing to appropriate the funds needed to allow the military to mitigate a larger portion of the perceived risk. Dollars drive the procurement actions (to include military personnel and their training) that produce a balanced (or out of balance) joint force.

In order to change the attitudes of those who approve budgets, the military needs to do a better job of identifying the spectrum of risk that various funding levels engender. As McMaster points out, the business notion of waste (as found in LEAN thinking) does not apply as directly to the military. A larger, balanced force structure inventory than immediately necessary (one that is able to handle more than just the short term, quick and dirty deployment, but not so large as to win WWIII within a week, a month, or perhaps even a year) is really a cost avoidance strategy, not waste. This is what needs to be made apparent to those who apportion Federal funding.