Luck factor is always there and is always important. I'd rather do shit in all my games, but get 4 other teammates that are overperforming, than being me who overperforms and having 4 shit teammates.
Now, the luck factor seems more oppressive when you have played few games. Like, you only played 100 games and you only managed to get from silver 5 to silver 2, because you had trolls in your team and only got, I don't know, 58% winrate. As you keep on playing more games, you will see that luck isn't much of a factor, as eventually the enemies will have more trolls than your team (9 other players to fill, 5 of them are enemies, 4 of them are yours, chances are, enemies get the troll more often than you).
This means that eventually, it's all a grind, since eventually, after A LOT of games, it gets to even out more. The more you play, the more it evens out, so if you're consistent with your play, you will eventually climb.