An interesting example from Morningstar that investing in the top 10 US companies in 1986 didn’t beat the stock market. This is another example of the historical difficulty of the top 10 companies by valuation to remain in the top 10 over 10 or 20 years.
Given the popularity and strength of the big technology companies today, it is difficult see what would happen to make them less valuable. (Not least as a capex heavy cycle in cloud have helped the largest companies, and that could happen again with AI). But historically there has always been change at the top.