The best ETFs and mutual funds allocate more value to attractive-or-better-rated stocks than the worst, which allocate too much value to neutral-or-worse-rated stocks.
In the worst case, this continues to the point that the consequences of success can be worse than the failure you tried to avoid: What is the value to achieve something that is inconsequential, and nobody cares about?
The best ETFs and mutual funds allocate more value to attractive-or-better-rated stocks than the worst ETFs and mutual funds, which allocate too much value to Neutral-or-worse-rated stocks.