As the majority of the investment community is aware, low cost index funds such as the iShares CSPX are a great way of investing your money in such a way that it will beat inflation and any other factors that will reduce the overall value of your money. Warren Buffett (CEO of Berkshire Hathaway) is notorious for recommending low cost index funds to those who are inexperienced in the stock market and even long term investments. There have recently been many arguments that made me question the integrity of this seemingly flawless investment ideology. Even Buffett said the "only" downfall to index funds is that they are, and I quote, "boring". These arguments that have sparked up across the internet are by those who fear that the inherent price of these index funds are far beyond their actual value despite them holding the top performing stocks in the market. Thus removing the need for investors to investigate individual companies and rather stand at the sidelines and say "Just buy them all and see what wins". This attitude towards index funds and the ludicrous prices/growth (in comparison to any other listed entity and their own past) has sparked major concern. I have provided a link to a video below that discusses the 2 opposing ideas presented by Warren and Michael Burry (Famous for his prediction of the stock market crash of '08) and what each of them mean. From my view point (albeit mildly inexperienced) has led me to believe that in the long run despite the concerns, there will be crashes, like every other market ever, but these crashes will be shrunk by the overall growth in the following years and or decades, therefore making it worthwhile to invest in such index funds while dedicating at least 5% of your portfolio in individual stock.
TL;DR: It is inevitable that there will be a crash in all index funds at some point or another (that cannot be changed) but in the far longer term view, it will still be worth your time, money and effort to invest in such equities.