Those who said the goal was lucky didn't seem to accept Arsenal defeat. A single goal isn't enough to prove Liverpool played well, but on paper Arsenal only managed one shot on target. Arsenal front line couldn't penetrate Liverpool solid defense, which is why Liverpool were stronger than Arsenal. Gyokeres, Madueke, and even expensive new signings like Eze didn't pose a serious threat.
I don't see any reason to say that Liverpool won because of luck. Dominik Szoboszlai scored a great goal from a free kick. It was definitely a great goal. At the same time, I would say that Arsenal lost because of their poor finishing.
Although Liverpool didn't play well in the first half, Arsenal performed well. Especially, they created several great attacking opportunities. At least they created three easy scoring opportunities in the first half. But their finishing was much weaker. And Arsenal's overall gameplay was weaker in the second half. Liverpool definitely won because of their good performance.