People improperly conflate public active funds, which are not incentivized to outperform, with all portfolios. Funds that consistently outperform for a very long time almost universally end up closed or are prop trading shops, the latter which would have no reason to exist if they
didn't outperform. All of these have practical scaling limits but it isn't inordinately difficult. Only comparing indexes to public active funds is a bit of a straw man because it actively selects for under-performers.
I'm a long-term risk modeler, originally for fun and later for profit. I build portfolios of US large caps based on categories of risk that are not priced into the market because they are difficult to model in a conventional way. This is an entirely uncontroversial way to outperform indexes but you wouldn't build a public investment vehicle around it. My oldest continuous portfolio goes back to the turn of the century, at around 20-21% ARR (more recent portfolios are a bit better). Per year, it requires maybe several hours of my time. I have a few friends and acquaintances that seem to do a bit better (but also spend more time on it) that also trade on un-/mis-priced risk, often as a justification to polish their data science skills, across a variety of asset classes.
I am not saying it is trivial to consistently outperform the indexes, just that the difficulty is significantly overstated. The hurdle most people trip over is that there are no shortcuts to figuring out how to build your own models from first principles and how to trade them.