It is great to see a modern portfolio theory shop like Morningstar admit that momentum beats the market handily over time. Of course you then would expect them to try to find all the flaws in the data. No investment strategy is perfect. No investment strategy will work in every environment all the time, they all experience drawdowns at some point and will underperform at others.
To just lump momentum investing into one bucket is like lumping stock investing into one bucket. There are a number of different ways to pick stocks just as there are a number of different ways to implement a momentum strategy. For example, what will my basket of securities be, what constitutes a measure of momentum, what time frames will I use, etc?
All the research clearly shows that there is something to momentum just like the science in the middle ages clearly showed there was something to the theory that the Earth and planets revolved around the sun. Instead of sticking to the accepted dogma to say that momentum can’t really work as well as advertised because it would invalidate everything else we hold to be true, a better approach would be to study different momentum strategies to see if the simple stratgies that were studied can be improved upon (hint: yes they can).