> My personal performance of investing in all three categories (total market index, S&P 500 index, NASDAQ-100 index) matches every chart you can find online over last 5 years; the total index funds are carrying the baggage of all that "not S&P" weight and are worse returns than the 500, with the 100 achieving almost twice the performance as the 500 (near 24% returns over 5y).

I think you're perhaps inadvertently proving my point: If S&P funds are performing significantly better than total market funds, either there's something particularly special about S&P companies (very valid reasoning, it's not a random assortment) or S&P companies are overvalued simply because they're part of the S&P and investors value that more than perhaps the fundamentals would support (not a completely asinine thought).