As anyone who plays competitive sports or games knows. Luck is indeed a major factor in winning. However the kind of "luck" that is, is different from what people normally think of.
When you think of "being lucky", you often think of stuff like "if I hadn't sneezed, I wouldn't have stopped moving and the falling tree branch would have hit me". There's no control over it and it feels like if you "win" it had nothing to do with anything you could have done.
But actually the kind of luck relevant here is more like.....there's 100 opportunities in a given match. A lot of these are hidden or "locked"...you need to do something to unlock them. People train themselves in a game or sport so that they start to spot the hidden opportunities, or lay the ground work to unlock them. Good players and teams access a moderate number of these "opportunities"...and these start to become "known tactics". The average baseline of what you can access is known. Let's say it's about 40~50 out of the 100 things.
Every now and then...there's a team that goes one step further. They're highly adaptable, very instinctive, yet disciplined enough to make even the most cobbled together plan work largely smoothly. This team sees more of those hidden opportunities. Maybe 70~80 or even more. Then they have the guts to take them. And then they have the coherence to act on them properly. That is what Miho and Oorari are. That's luck because in the end the opportunities are just potentials and they're also not always there. But it takes a very special kind of team...and leader....to always find what's there and act on it.
In the end a team that is merely very well trained never goes beyond the 40~50. They're trained to lookout for only that much, and only act on that much. It's not wrong...this is how you manage to get especially large teams to work together smoothly, and do what they know how to do very well. In fact Oorai's method is complete anarchy, the downside is they approach even the simplest things in that ad-hoc manner (though they fixed a lot of this by the movie period)....it's not a stretch to say how they do things only works because of Miho's ability to organize and strategize on the spot.