Fantasy Football is indeed a game with a ton of variance and uncertainty. Sixteen games is a tiny sample size. Players get injured, players run hot / cold, even something completely unpredictable or unknown is a possibility. "Any given Sunday" is applicable to fake football as we all know.
The "luck" and "bad luck" people speak of refers to the fact that we cannot control what the players do. We do all this research and do our best to start the best possible lineup, but in reality we cannot control the outcome at all. It's like every time your player gets locked-in to the lineup, you're "all-in" pre-flop in a hand of poker.
We all know the story - your stud lays an egg in an ezpz matchup, and you lose by a couple points. Stats say this happens all the time. The rational side of our brain knows this fact. However, it's hard not to feel a type of way about it. Control is a big part of why FF owners feel this way (rage lol). It's like getting sucked out on in poker when you shoved with the best hand. In FF we "bet" on players performing well. Sort of like the stock market, or an extremely sophisticated horse-race bet ha.
Also, it's very easy for us to get self-absorbed in the misery of our own bad luck, but I guarantee if you look closely at the history of your leaguemates most have been through the ringer too mate.
That being said, FF is far from being void of skill. Drafting, waivers, team / roster management, analytical skills, research skills, all heavily contribute to W/Ls. Likely more than poor, outlier performances at the end of the day. Hell, all of you here doing research everyday have an edge over the owners in your league who don't. You have to put yourself in the best possible position to win in a sea of uncertainty and it's easier said than done.