Not only do you get on average better returns, you can do better even when they perform poorly since those funds (in Canada) can charge you anywhere from 1.5% to 3% of your portfolio in fees (MER), while an index fund could charge as low as 0.1%.

https://www.wealthsimple.com/ (I'm a customer) has recently expanded into the US from Canada and are one of a group of what is being called Roboinvestors which take these index funds and let you easily invest in them.

Wealthsimple adds on 0.5% fee which is still lower then active funds, my portfolio has a weighted MER of 0.64%.