Your last sentence is terribly wrong, and unfortunately, many people share that mistaken view. Let me explain...
Active managers go around with the notion that as they die off to be replaced by index funds, that there there will be no price-finding.
But here's the thing - before managers, and before mutual funds, most people were buy and hold investors. There was very little "price discovery" compared to today, as most stocks sat on a shelf (literally, as people had paper certificates for the shares they owned).
In that world, the price discovery function was quite small, but clearly adequate.
Today, there are many highly-paid managers who "actively" manage money. ( I challenge the "actively" portion, because many are closet-indexers. If you google "active-share", you can find more about this.) But even if they aren't closet indexers, in any given year, most cannot beat their benchmark. When they can't beat their benchmark (which, ironically is an index), they are inefficient.
That statement bears some emphasis - When Active managers cannot meet or beat their benchmarks, they are __REDUCING__ the market's efficiency. Put simply, they were wrong on what they thought the correct price should be, thereby hindering price discovery.
Read that last paragraph again - it's extremely important. Also, note that there are many people on Wall Street who are highly compensated, and afraid that their jobs will go away because of indexing (note that the S&P 500 is only one index - there are hundreds of others, including MSCI and Russell indexes). They are right to be concerned. After all, as in anything in life, if you can't keep up with the benchmark, you will get cut. This happens in professional sports, people in college with poor grades, and anybody in a sales job. And it's been happening in finance since before any of us were born.
One final note: Back in 2001, the US markets moved from fraction pricing to decimalization. In short, the price increments went from 1/16 of a dollar to 1/100 of a dollar (i.e. a penny). That's a six-fold improvement in pricing accuracy. To think that having less active money will destabilize our economy is unfounded.