Why is ETFs more optimal than mutual funds?

Traditional mutual funds appraoch was to do a lot of stock picking analysis to generate "alpha" (fund manager excess return).

It turns out there is a broad body of research showing it is very hard to generate alpha consistently, particular after factoring the cost of all those (high paid, questionable value?) stock analysts.

So lately ETFs have come on the scene where they instead aim to just copy the index but at a low fee and so can beat (on average) returns from mutual funds.

The main benefit of ETFs is that it aims to mirror a broad base of assets with a lower fee. If you are purely looking at saving cost and to start investing, this might be a good place to start. But do bear in mind, low fees do not necessarily mean better performance too.