although low cost has proven to be the most consistent and effective quantitative factor that investors can use (ex-ante) to noticeably improve their odds7, it does not, by itself, guarantee success
In liquid markets it's the number one factor and takes basically no time at all. Any Joe Schmo can do a basic version, just buy the Wilshire 5000 and move on. If you're feeling more advanced, throw in some international indices, maybe some bonds too. But it takes basically no time at all and you can move on to whatever else you do for a living, confident that you will do better than most actively managed portfolios.
Are there better choices if you want to spend more time? Sure. Invest in something where you genuinely know more than everyone else, like local real estate or your brother's business. The risk is higher too but you can capture something from knowing more. Goldman Sachs doesn't have anyone assigned to cover the house down the street, but you might be able to make something off it.
But unless you have a net worth in nine figures or so there isn't much point in trying to eke out an advantage by researching well-covered investments in highly liquid markets. That's a game for the big boys.