What are the ramifications if everyone followed professional financial advisers’ advice and just invested in funds like VTI?

Let's not say “like VTI”, instead let's say only VTI. Let's take this to the extreme to understand the possible ramifications better, let's say everyone and I do mean every. single. retail. small. investor. followed that professional advice, that we're too dumb to pick stocks and it's best to diversify, so we give all of our dimes to Vanguard and put it into VTI. What are the ramifications of doing this? How does it affect Vanguard? How does it affect the market? How could this knowledge and trend be leveraged by fund managers and companies? How could this be leveraged by governments, the Fed, bankers, etc. (monetary and fiscal policies, interest rates, quantitative easing/tightening)? What would this mean for our returns over the long haul? What are the ramifications?

Edit: If you downvote or upvote would you please share your thoughts?