So anybody who knew in advance that, for some inexplicable reason, the broad US market was about to become more and more and more expensive, good for them. For those who were merely along for the ride and got lucky (essentially everybody owning the S&P), I don't think there are any bragging rights to be had.

I am less dismissive of those who have achieved success investing in the index. For the past 15 years there has been non-stop commentary about how the index is overvalued. In the face of this relentless convincing negative commentary, those who nevertheless continued to dollar cost average into the index, year after year, decade after decade, and never sold, deserve kudos and I would say have definitely earned bragging rights. Being able to do this and not be shaken out along the way is not small feat, and cannot be attributed to just pure luck. It requires a well thought out investing framework. It's a decades long bet that when you sell far into the future during retirement, again over time, you will on average realize a pleasant positive real return. Once you realize this key insight, it becomes easier to ignore the valuation commentary even if justified.