The ETF is the sensible default for a reason
A broad index ETF gives you instant diversification, tiny fees and the long-run growth of the whole market with almost no effort or skill required. For most people, most of the time, it is the correct core of a portfolio. Any honest discussion of alternatives has to start by admitting that the boring index fund is very hard to beat and should rarely be abandoned.
What an ETF cannot give you
An index fund has two built-in limits. Its returns are tied to the market, so when stocks fall broadly, your ETF falls with them — exactly when you might want something that does not. And it is passive by design: there is no edge to develop, no skill to compound, just the market's average. That is a feature for most savers, but it leaves a gap for anyone wanting returns that do not depend on what the stock market did this year.
Where a skill-based alternative fits
A data-driven sports portfolio sits at the opposite end on almost every axis: active not passive, skill-dependent not automatic, uncorrelated to equities rather than tied to them. Its returns are riskier and never guaranteed, but they come from a completely different source. That difference is precisely what makes it useful as a complement — it can smooth a portfolio that is otherwise entirely exposed to one thing: the stock market.
The combination, not the choice
The strongest setup for most young investors is not ETF or alternative, it is ETF plus a small alternative sleeve. Keep the index fund as the core that does the long-term heavy lifting, and add a modest, well-sized allocation to a higher-skill, uncorrelated alternative on top. You keep the reliability of the market's average while giving a slice of your capital a shot at returns the market alone could never provide.