Should I just invest in index funds? I heard that most investors can't even beat the market by buying stocks?

Yes, of course. VT or SWRD could be nice.

Most active fund managers don't tend to outperform the index net of fees. But all index funds don't outperform the index either.

There is another case when comparing to markets out of US. The markets tend to be less efficient and active managers usually can perform better making active choices.

Index funds are great, but there can always be space for active fund management to be in your portfolio. Especially in harder to access geographies, specialist sector funds, other asset classes such as bonds and commodities.