During the years I have warned investors about blindly investing in a "sexy" ETF idea without first understanding the underlying index and how the fund works.
One thing that investors need to understand is that ETFs were primarily trading vehicles. They are not, or at least were not designed to be long-term investments hoping to generate alpha. To a sponsor, the primary goal is to gather assets while following the index. It's not to generate alpha, to provide above market returns or to preserve capital.
Another concept that goes hand in hand with this is