Well, index funds are also the only way for the average person's portfolio to appreciate faster than inflation. Remember that even most professional traders underperform compared to S&P500 in the long term.
Now if the funds you experienced were actively trading rather than just buying Index ETFs, that's definitely a scam.
Before I turned mine here in Estonia from a composite index fund into a trading account, it held US, european and world stock ETFs. Now I'm holding european, Asian emerging markets, China ETFs and some individual Estonian stocks that reliably pay dividends. I ain't keeping my shit in the US with Trump in charge.
NASDAQ 100 just got changed to completely fleece everyone who holds it next month though. Interest Free Loan With No Repayment Obligation To Elon Musk, inc is going straight into the index when it IPOs lmao. As will ClosedAI and Anthropic when they IPO.