Rather than looking at returns in isolation it might be more interesting to look at returns vs. P/E or vs. some other parameters like interest rates. e.g.: https://www.alger.com/AlgerDocuments/AOM_singleGreatestPredi... This is only a 20 year period which is pretty short, but hey, doesn't look as random any more.
The implied decision is whether to invest over the next ten years, and the chart implies that you can make this decision every month.