Stocks are kind of the "beginner's" asset. They're fairly easy to understand conceptually. "Trading" them is even easier. However, trading them in isolation for a profit _consistently_ is very difficult or just a product of luck. I don't know anyone who does it and wasn't burned eventually.
The thing to remember is, people doing funds or "trading" professionally aren't just buying and selling FANG stocks all day. They're balancing these trades with futures and options or options on futures and other alternative assets. They're hedging their positions and setting themselves up so that their probability of coming out ahead is much greater than you're standard "it either goes up or down" stock movement.
A simple example is the "wheel" strategy in options. A short put at a .30 delta on the underlying, assuming 1 stddev movements gives about a 70% chance of collecting the premium without assignment (of course this isn't perfectly true, it's an approximation). This is already better than buying the stock, which under the same methodology, would have a 50% chance of profit (either going up or down from the purchase price). When assigned, turn around and open a short call against the assigned shares at a similar delta and repeat. In the flat market we've seen the last year or so, this is reasonably profitable and very low effort.
Edit: The reason the "buy and hold an index forever" strategy is recommended is because it's the lowest effort, highest probability of profit strategy one can probably take. I agree with it entirely for 99.9% of people. But that's not to say there isn't other opportunity out there if you're willing to learn about it.
Source: spent a few years at the Chicago Mercantile Exchange working on these sorts of things exchange side and now trade regularly on my own.